TGF is great for most game related things, but it does have a few limitations here and there, which MMF generally doesn't have. I upgraded to MMF a while ago, and haven't regretted it in the least (with the exception that the TGF graphics editor is strangely superior). If you're unsure about spending the money on MMF, try the demo. It lasts for 30 days, which should be enough to get used to the interface and learn about the neat things it can do.