This is an interesting topic to me, for a couple of reasons. Firstly, because I think a lot of offensive choices are influenced by region. I think teams in Colorado tend to run different offensive schemes than a lot of other places due to the influence of CU-Boulder and Bravo, whereas places like the West Coast definitely have a different "meta-game" for their offensive stacks, as I'd call it. Secondly, because after the conference championships this past weekend, it seems that our Colorado "meta" may be shifting away from the Horizontal/Split stack, that has been a pretty big part of Colorado college and club ultimate for many years.
Let me preface this by saying, I can't for certain say what different teams are specifically running, when and why. What I can tell you, is what I've observed, having been to club and college nationals, and having participated in tournaments in every corner of the country.
The first stack I learned as a college player in 2003 was a center stack. It wasn't our offense at CSU, but it was used as teaching tool, for people to learn how to make a good solid cut, to learn timing, and because we ran a center stack as an endzone offense. In Colorado, for a number of years it was generally regarded as an inferior stack, because it was easy to poach and went very stagnant from the sideline (I'm not calling it inferior now, wait for me section on that below).
Our actual offense my first two years at CSU was a horizontal stack. The standard three handlers back, four downfield, using all the horizontal space, working the complete field width with handler swings etc. In my mind as a young player I regarded this as a top notch offense, mostly because it was most of what I had learned, and our team ran it well. It wasn't until Potlatch in 2005 that I began to realize that the Ho-stack is much more of a beginners stack and that it was cycling out of the competitive college scene and club scene quite quickly.
At Potlatch my club team, DTL, had won the services of the Team USA coach Ted Munter in an Ebay auction (fundraiser for Team USA), for one game. After dressing him up in a sweet red jumpsuit with lots of bling, he coached us for a game, then gave us some great advice on how we looked. The thing I remember most is that he told us that Ho-Stack was really a basic offense; easy for a smart team to shut down, and the advantages were almost non-existent versus a split stack or a spread stack.
After that year, at CSU, we moved on to a CU/Bravo-esque split stack, and have not since returned to horizontal. What sparked my interest in this topic, as a mentioned above, is that this past weekend at the Rocky Mountain Conference championships both CU and CU-B were both running exclusively a center-stack, and while they've used it on occasion in the past, I don't believe it has ever been their exclusive offense prior to this year. This got me to thinking about the different advantages and disadvantages of the 4 stacks I'm spent the majority of my ultimate career playing, and why more and more teams seem to be changing to center stack.
Note: I'm not going to describe in detail what each stack does, if you aren't familiar with it, check some online resources.
It's a great beginner offense. Everyone has a position on the field that is essentially theirs. You stick to your cutting lane for the most part, are looking for big handler swings, and the emphasis for the downfield is mostly "run your ass off, and don't stop." There's obviously an element of timing, like any stack, but foremost you're getting your downfield to truck it around.
Another big advantage is that you always have an opposite side of the field from the thrower deep look. No matter where you are on the field, there's a cutter downfield in the far lane that has the potential to be cutting deep for a big, space deep throw (the best kind of deep).
It is easy to bracket the downfield; posting one defender as a deep and one defender on the under and just switching as the two cutters go under and deep. It's also very easy to clog the downfield with poaches from the handlers, as there are three handlers back at all times. Additionally, as the disc moves to one side of the field, the opposite side defenders can recognize that their cutters aren't primary looks, and interfere with both swings and deep looks.
Regardless of the ability to switch or poach against this offense, the biggest disadvantage that it has is that none of your cutters are given significant isolated space. At most you have 1/4 of the horizontal field to make your move as a downfield cutter, and even then, your deep is easy covered by other cutters' defenders who are not in a primary cutting position. In my opinion every good offense should give a primary look to a cutter with a majority of field space over any other cutter. As the overall athleticism in the game increases (and I believe in the last 8 years, it has increased RIDICULOUSLY in college), cutters need more space on the field to get open.
Overall, I think it is still a great offense to teach in High School or to use with newer players in a summer-league type situation.
This is a stack that I've run on every single team I've played on as a pull-play. It's very simple, it gives every cutter the entire field to get open, and it makes it easy to learn timing as you have a set cutting order and you know exactly when you're planning on cutting.
As a thrower in a V-Stack you can easily break the mark because there is almost 40 yards of horizontal empty space, even upside throws are viable because the cutter is always isolated in a 1on1 situation.
You have to start in the middle of the field for it to work. The reason it's run as a pull play, is because it's takes advantage of the fact that a defense is not completely settled in on their men after a pull. You almost always have an opportunity to center the disc off the pull. If you start the disc on the side of the field either you're behind the stack, giving you very few options, or you're on the far side of the field from the stack, where you aren't give the liberty of a throw wherever you want on the field.
Additionally, teams can oftentimes poach the underneath and deep with smart switches. One of the most effective ways of interfering with a V-stack is simply getting down on the pull very slowly, and thus clogging the cutting space for the initial look.
Overall, I still a Boston is one of the best pull plays around. The defense has to do something to interfere or the chances are good you will end up with a quick score for your team.
You are giving two cutters (the hot side) 2/3+ of the horizontal space on the field to make their cuts. As the disc advances downfield the cold side is cycling in from the far side of the field from the disc, essentially, turning it into a V-stack, which as I discussed above is extremely difficult to cover man-to-man.
You aren't completely crippled setting up on a side of the field, rather than in the middle, because you have two options as a primary look, so you are always given a break option downfield in addition to a primary deep or underneath cut. Really what this boils down to, is it's V-stacks little brother, set up so it develops into a Boston, but so you are able to start without the disc in the middle of the field.
The cold-side defenders can easily poach and interfere with the hot-side cutters as they recognize that their cutters will not be initially active.
You are allowing for handler poaching as well given that you have three handlers consistently behind the disc, making force-middle poaches and whatnot viable defensive looks.
If the disc ends up behind the cold side of your stack the downfield is very clogged.
Overall, I think split is still a very strong offense. All of the poaching issues can be managed with good handler movement and good cycling from cold to hot, and it allows plenty of space for your cutters to be isolated.
You are leaving either side of the field open for a break regardless of the force. You are giving your primary cutter the leeway to make any cut they want, deep, underneath, break. You are allowing for a reset (the front of the stack) that will always gain yards, rather than other offenses relying on a backfield handler cut. The person who is your traditional dump reset (assuming you run only two handlers back as a default), also has the entire backfield to set themselves up for a continuation break throw.
This is an offense the needs to start in the middle of the field, however the are plenty of easy options for the middle reset.
You are susceptible to poaches underneath from the non-active stack members.
You need a lot of speed in your cutters. While most teams that run center stack can call any number of set plays (Santa Barabara comes to mind) a good chunk of the time the first cut will be coming from the back of the stack, so they need to be able to cover a lot of ground quickly, to give you a viable option from the get-go.
You also need handlers with BIG arms. Since the back of your stack is set up fairly deep compared to a horizontal or split, the people you have picking up the disc need to be able to put the disc 70+ yards from a stationary position. Additionally, your throwers need to be able to break the mark liberally. You have the entire break side of the field open for floaty breaks, so your throwers consistently need to be able to make that break throw. Much of the success of a center stack depends on getting the disc around to the break side of the field then continuing breaks down the field.
Overall, I think center is becoming (I realize a lot of college teams, especially west coast, have always run center, I'm taking this from my Colorado perspective) the stack of choice for elite college and club teams. You are simply given too many devastating options when you have the speed and throws to take advantage of the strengths of a center stack. A lot of the most athletic teams I can think of in both college and club (Doublewide, Mamabird, etc) now seem to run center, and it is obviously successful. It's a hucking and break-mark offense, and if you have the throwers and big downfield cutters to pull it off, it's next to impossible to defend. A far cry from the "noob" offense I was taught it was eight years ago.