fantastic Explanation. This is such an education for me and a humbling one ta boot. My puny little mind was telling me that people into dance music don;t really care too much about tone and sound, as long as the bass kicks. The W3's really shine in Rock and Hard Rock, blues and so on.
The main difference between the superb W3's and the even better I.M.O Sm3's is the mid bass and Highs . The Mid bass hump on the W3's is not there on the SM3's .And the Highs are not so prominent on the SM3's as the W3's .
Imagine the V shape that represents the W3's frequency signature .In direct comparison the SM3's are simply not as V'd and don't have that extra added mid-bass hump . This also brings out more Mids which you may like or not (but of course the SM3's freq signature is not an inverted V as this would sound very ..... technical word..crap .They are just less V'd than others) .For example adding lots of bass and highs on a EQ will veil the mids because all that is being added is actually volume and not quality /clarity.
What led me onto the SM3's from the W3's was initially that Mid-bass hump over production of the W3's . With some tracks I noticed a over production in that freq area, even compared to Big headphones like Audio technica M50's . The SM3's definitely reproduce the bass more evenly than the W3's whilst still giving the depth of lows like the W3's .
So my advice is if you don't have the means to do a direct comparison and if you personally don't have any issues with the W3's ,then your not missing out on anything other than a different frequency signature .
For me personally that Different freq signature of the SM3 was the slight difference to one part of the sound that made a Big difference to the whole .
Hope you catch my Drift