If you're gonna use acrylics, go with Vellejo. They are engineered for
figure painting and work really well with a brush. That's what all the
master figure painters who use acrylics use.
The rest use mainly oils, which is my choice. Oils are ultimately
easier to blend, but they do take a day or so to dry fully. There are
ways to accellerate the cure time though. I use Vellejo for my base
coats and then paint the oils on top.
Bill Horan uses Humbrol almost exclusively, with some oils for deep, rich shadows.
Ultimately, the rule of the road is whatever works, so if MM works best
for you, then that's the ticket. You should try some things out though
first, to see what works, and get some figure magazines to see what the
best are up to. It's a good motivator and gives some incentive to keep
working to get better.