Couldn't tell you about the 1/2000 kits, but the Seed EX kits of Archangel, Minerva and Argama are awesome.
Dendrobuim is a total MUST own for a Gunpla builder. 3 feet long, massive, and really, really good details. Fits in nicely with the Fix Fig Deep striker and Stamen also. And it breaks the tediousness of building just a MS.
All in all, if your a big MSG fan, and love WB, then by all means get the 1/400. Just don't pay an insane price for it, because it's not worth it.