This seems like stating the obvious but really an important statement.
I have owned all Westone universals except UM1 and to me it seems Westone is always very aware of making sure their IEM's have sufficient bass or bass impact. UM2, W3, UM3X and W4 to a certain extent all have ample "weight" to the bass and they don't distort!. For anyone finding the W4 bass lite...I am using "jazz" eq setting on Ipod Classic which just slightly tips the bass and treble upwards. Some of you may cringe at this premise but I think it adds some excitement to the presentation without screwing anything up.
Hard to imagine UE900 vocals being even better! Just listened to the entire Diane Krall, Live in Paris (superbly recorded cd!) and was mesmerized even though I have played it 50-60 times previous. It was better than being their live...no kidding either.
W4 is the only universal in my signature that is clearly a step up from my JH5 which is saying a lot. But this goes back to personal preferences too.
I appreciate all the comments and contributions on this thread. Good stuff. I think, I too, would have to take UE900 off my short list of future purchases even though I'd still love to try it out.
Westone W4 does vocals better, I think I said that in my comparisons as well (another member said the vocals on the 900 are better, but I don't entirely agree with it :p). The UE900s more neutral than the W4 (neither are neutral though). You are right with you assertions about bass though concerning the W4. It has a nice weight to it ;)