There's a product here on the RMP called the UMT (Universal Morph Transfer). It's a godsend because you can use morphs for any of the unimesh figures on any of the other figures. M3 and V3 end up looking awesome with David's muscle morphs... Also, from a more practical point of view, David poses better and morphs better than M3 does, especially when you start adding muscles (M3 has horrible shoulders). M3 on the other hand has about four times the clothing (especially sci-fi clothing which David is sorely lacking). S3 is far less versatile than V3. I've made V3 look like several different people I know and have also been able to duplicate their body shapes pretty accurately as well. S3 simply can't do that because she starts off with a very weird body shape that does even weirder things when you start moprhing it.