It isn't very significant, but here's what I can think of:
- Obviously, you play as a girl in MFoMT and a boy in FoMT.
- Going with above, again obviously, in MFoMT, you marry a boy. In FoMT, you marry a girl.
- MFoMT has two more marriage candidates, granted you'll probably never even consider marrying them...
- The dialogue differs slightly because of the gender difference, and the translation of MFoMT is a bit better.
- I think there's more random events in MFoMT.
- New items in MFoMT. I can't remember their names, so I won't name them off.
- You can change the color of your overalls and a couple other things in MFoMT.
- Probably one of the slight tweaks that matters the most: If you befriend Won, one of the secret bachelors, to a certain level, you can start selling things for higher prices to him. Probably one of the best ways to get a truckload of moolah.
And some other minor stuff. In a short, MFoMT is the better game. However, overall, the choice between the two is mainly asking yourself if you want to play a girl or a boy. :x