Very few. ..

G70 is lighter (go figure!)
G70 has separate outputs for the harmonizer section
G70 has a pair of Aux outputs, to route any Part (except the B3 sim, dammit!) off to it's own output. This might not seem like a big deal, but you can route the G70 Aux outs back in to the RCA inputs, which have their own IFX full effects section, and gain another independent insert effect on any Part you want - an opportunity lost on the E80)...
G70 has more legacy patches from Sound Canvas days (but fewer new patches)

That's about all I can think of..