Very different beasts, perhaps close to total opposites. W3 is v-shaped and has a very dry, neutral midrange, peaky treble, and really loud midbass. Good for electronic music and some metal but not much else. SM3 is a beast of an all-rounder that has a warmer, darker tone, forward mids with very flat, well-extended bass and smooth treble.
Both are really good with electronic music, but the SM3 plays well with acoustic, pop, most rock (metal is not so great but indie and alternative do well), most classical, hip hop (as long as you don't need THUMPING bass), jam, jazz, blues...almost everything. I found the W3 really only useful for electronic music; metal is tolerable as guitars have good crunch, but vocals are so overwhelmed by bass that its not truly enjoyable for me. I will say this: it makes electronic music sound the closest to a live show of anything I've heard, which is to say the soundstage is good, and the bass is heinously loud and a bit rolled off.
Edited by Gilly87 - 6/16/13 at 11:20am