Assuming you mean the Radio by Spektrum?
Well, I'm currently a 6i owner, (so no reason to upgrade), but It's the radio I'd buy if I were taking up the hobby.
Main reasons being:
-my 6i has served me very well, and the 6 is a step up in features. Might as well get "this years model"
-compatibility with Horizons line of ultra micro planes (which have the RX hardwired in).
Just my $0.02
All this is assuming you mean the new 6' (the black one), there is also a "DX6" that pre-empted the 6i, but it's not compatible with the latest Spektrum technology, and has been discontinued for several years now.