The bottom line is, and should be, that the SM64 is a very awesome listen, and I would bet the vast majority of people would pick it over the W4, especially if they are trying to get away from neutral and boring. SM64 is one of the most engaging listens under $500 bucks around. That, and the Flat4 SUI, and the FAD Heaven V. All measure very poorly, all have dedicated followers. You like the Flat4 yourself.
The W4 is a fine earphone. No doubt. I owned it twice. At the end of the day, it's preference. And the OP wants to get away from the W4 whether it measures better or not. For the OP, the SM64 is what the doctor ordered. And for many other people, it is nothing short of a fantastic earphone in its price range. Because it is.