Chou, why on earth do you think BW was the most diverse meta ever? For a long time, a large portion of the ladder was essentially endless variants of Rain teams and I personally felt that DPP provided a much more varied mix of play styles/viable creative sets.
You just answered yourself, shooting yourself in the foot using the word "variant" (as in various, or variety) in an argument that there is none. Every VARIANT of rain means more variety-- Ferrothorn hazard rain hyper offense, Tornado spamming offense, Rotom-focused volt turn rain offense, rain STALL (a highly popular team that's dead and gone now obviously), Set up heavy offensive rain with Dragonite and Toxicroak, etc. etc.
Also you and I both know that rain was king at the upper middle of the ladder, not at the top of it. Sand, Sun, and Deoxys (while it was around) also gave rise to as many different varients-- offensive and defensive-- of their own playstyles.
A great many Pokemon we banned also were central to styles that would exist in a metagame that wasn't artificially altered by us. It's easy to argue that the variety of a generation should be judged by what's actually in the cartridge, not by the shape of our own meta-- after all, judging the "variety" of a generation is a critique of GF, not of Smogon. So while BW OU (even as we shaped it) already had a great diversity of play styles, there were also a great many that also would exist where Excadrill, Landorus-I, Sand Veil Chomp, Swift Swim Kingdra + Toad, Tornadus, etc. etc. also exist.
3 different weathers fighting it out in OU, each giving rise to their own variations of offensive strategies and defensive strategies, the longest list of OU Pokemon ever, and a great number of UU, RU, and NU mons ranked C-B in OU viability (something that absolutely would not exist in DPP)--
No matter how you look at it-- # of team variants, # of team arch-types, # of OU Pokemon, # of Viable Pokemon, # of strategies developed over the gen, # of creative gimmicks invented in the tournament scene-- BW totally outclasses DPP and every other gen in terms of diversity. This isn't even worth debating because it's just plain fact.
When DPP was the major official meta, everyone constantly bitched that OU didn't have enough diversity. When BW was the major official meta, people began to bitch about how too much diversity (too many potential team match ups) was the source of not being competitive.
BW was definitely not the most balanced gen... but if we're talking about the creativity sparked by BW compared to DPP, especially looking at the play of top players in each gen-- the difference is obvious.
Edit: In any case, this discussion is about XY, and let's try to keep it that way.
Diversity does NOT necessarily mean better or worse-- it's totally separate from that.
However, XY's currently greatly decreased diversity compared to BW does not need to be explained. Even the most unbalanced first round of BW (with Darkrai, Shaymin-S and the rest) had a lot more diversity than what exists in XY now.
