rather than post in your offense and defense threads...
the reality is, any set works. the trick is to have a strategic, well thought out system, of which the set is just one part. defenses matter a lot more than offenses (i guess i should have posted there, too late now), which i'm sure was true in your day - but its probably even more true now, due to the increase in the importance in fatigue. if you want to press, great, you have to focus on consistent depth though, if you want to be highly successful with it. if you want to run zone, great, but make sure you prioritize signing high end players over filling out your roster. its not really about the set, but about how you play it.
one of the big paradigm shifts in the "new engine" (which is 3 or so years old now, maybe more?), was the shift from speed dominating on defense in the press, to ath/def really dominating all over. ath and def are linked in recruit generation, and the importance of those stats has went up considerably, to the point where many consider high ath/def the defining characteristic of almost all great d2/d3 teams. under that light, i sort of consider man defense the "default" set, ath/def man teams are what emerged as dominant early in the days of the new engine. but really, any defense can succeed, you just have to focus more on studs in the zone and more on depth in the press.
on offense, the most important thing is going to be getting the right amount of high quality offensive players, who can carry much of load, so that you are freed up to focus on other things (def, reb, guard skills) in some of your other players. that truth overshadows the actual differences between the offenses. that said, the most unique offense is fastbreak, because it has a higher fatigue profile than the other systems (which are all about the same), and because it is best able to take advantage of non-traditional offensive players (not great lp/per players, who thrive off ath, spd, bh, and ft%). fastbreak will also result in 1-1.5 extra turnovers per game, roughly speaking, but all in all, its a lovely set. it is the set that, holding offensive ability (of the team) constant, allows for the best defense, rebounding, and guard skills - because you can do more with less on offense, allowing you to focus on those other things. its also a great set to pair with man or zone for high quality teams without much trouble filling up or coming close to it, because the additional possessions fb creates is similar to the additional possessions press creates, but maybe half as much in magnitude - they reduce volatility, which is always hugely important for high end teams. the thing i love about fb within the offense it creates itself, is that you can really do anything you want, and still do it extremely well. you want a foul-drawing based offense? fb is as efficient as any (slightly more so, if you exclude turnovers). you want a heavy 3 point shooting offense? fb is as efficient as any, and probably slightly more than any other offense, excluding turnovers. turnovers are the price you play for all the flexibility you could ever want, on the two main vectors - the type of offense you want (how many 3s, how many bigs, etc), and the range of players who can contribute efficiently on offense.
the other 3 sets are pretty similar. they have similar levels of fatigue, turnovers, etc... generally, flex is going to be your most guard oriented set, and relies on spd and per more heavily than bh. otherwise, i dont find much unique about it. motion relies on bh a little more for guard offense than the other sets (fb excluded), and is slightly more geared towards well rounded teams, and probably best takes advantage of bigs (fb excluded). triangle is a great set too, its kind of in the middle. i don't think it relies quite as heavily on ath/spd as other sets might, though. these differences are all pretty small and generally are all much less important than other fundamentals of team composition - like focusing on the law of diminishing returns (getting the right amount of stuff, like offense - enough to be efficient, where you hit that sweet spot, where having more offense doesn't really help much, it just mostly would take away from other things like defense).
mostly, fb and zone are the "black sheep" sets, but fastbreak is a great option and zone can be if you play it well, it just seems like it might struggle a bit at the very upper echelon, where great talent AND great depth can coexist. but in a short stint with zone, i've found it to be quite competitive at high d1 in general, where theoretically it is worst off.
anyway, ultimately, i think it really comes down to playing a system that is well organized, with good synergies and strategy built in to it, including how the set is worked into your system - more than it really is about the set you play itself.