If you're getting an M14, TM is the only way to go.
Have fun finding magazines, replacement externals or compatible internal upgrades for anything but the TM.
If you don't game, want something to ocassionally shoot in your basement or to hang on a wall.. Sure, go for the G&G... but any experienced player will tell you the same thing I did.
I've bought and sold over 5 M14s, I've got first hand experience working on
SEVERAL (I'm one of the only techs that'll touch V7 in Manitoba)