OK, I'm very biased towards the 8FG, as that's what I went with, moving up from the 9C.
I'm not a heli guy, but I know of one advanced heli pilot that favors the 8FG over the much more expensive 12FG (he has both). From what I have heard, the 8FG is more advanced as far as heli software goes.
The 8FG has the advantage over the 10C, in that the user can download updated software from Futaba. The SD card provides for almost 4000 model setups[:-], but more importantly, allows you to store your model setups in a folder on your PC, in addition to a copy on the SD card. The 8FG will be a 12+2 channel radio with the new software (the 12FG will be 14+2 with an update).
Just my 2 cents, but I think the 10C will probably not be in production for long[&o].
A couple of other good points on the 8FG. Full ability to assign any stick or function to any channel. Stock battery is 6 cell 1700mAh rated, gives about 7 hours of run time, and if you want to go lipo, the voltage is a perfect match with a 2S lipo, in fact units sold in Europe (Robbe distributor) come with lipo and matching charger. For neck strap users, the 8FG balances perfectly and is lighter in weight than older radios, a good thing in my opinion, since I use a neck strap.
The programming easy of the 8FG is a delight. When I go back to the 9C, I get all messed up
Good luck, no matter what you choose, you can't go wrong if you go FASST[8D]
Pete