I have both. Your question is hard to answer, as they are very different rifles, and it really depends on what you want it for.
Both are great rifles, IMHO, but if I could keep only one, it would be the tavor. Excellent ergonomics, affordable ammo, very reliable, takes 10-round mags, reasonably accurate, and lightweight. The trigger is mediocre, though.
However, if you want a rifle for hunting midsize game, take the RFB - excellent trigger, heavier round, decently accurate. Ergonomics of the bolt release and mag release are not nearly as good as the tavor, though. The only other thing I don't like about it is the fact that I can't check the chamber without removing the mag. Still can't get used to that.
Tavor's a bit more expensive than an RFB (by about $400ish new), and I've only seen them in black.