About 10% of my characters and work is with M4 and V4, another 10% is Genesis, 20% G2, 55% G3, and 5% other. I actually use Vicky 3 more than G8 and I won't even touch 8.1 or 9.
G3 is my go-to because it natively does everything and imports from everything. I can't get 8 to play well with 8.1, yet I have carnomoloch and res mortifera conversions to G3M? Enough said.
But V4 and M4 definitely have their place. They are the easiest to sculpt new morphs for, the easiest to distort and re-rig right in the app. Almost as easy as Genesis (1) to slap geografts onto.