It has nothing to do with that. How well Gamemaker in general performs varies greatly depending on certain elements of a system that can be very hard to change. My primary computer has a rather high end AMD Phenom II X4 processor and a moderately decent Radeon HD 5770, yet it grinds to a halt playing certain GM games that an old Core 2 Duo laptop will run at full frames with no effort whatsoever simply because on the one computer, an svchost container starts eating CPU like crazy. It doing heap validate calls over and over and it page faults like crazy. I'm talking like 35,000 page faults per second. On some GM games, they still run alright (notably Spelunky), but as they get more complex, it just becomes totally unmanageable. In fact, I can fix the performance issue just by killing the svchost process, but then Windows goes berserk, various drivers stop working including sound, and it tries to force itself to shutdown (which can be canceled fortunately). Unlike Linux there isn't really a good way to get stuff back to running properly afterwards either. I don't really know a proper fix. Oddly, just unplugging my mouse increases the frame rate by about 60% and
MMF2 has the advantage of at least being consistently shitty across all platforms.
That said, if compatibility isn't a primary concern, GM has way more control than MMF2 and its a lot faster to program with. I don't know if there is a major performance advantage... I've found pretty interesting ways of storing object references in MMF so that object selection doesn't become the obscene performance hit that it can be doing what people have traditionally done, but I'd much rather work in code than in MMF's cumbersome event format, especially when you start trying to do nested conditions which is a heinous pain in the ass with MMF.