I know the B7 S4 to B7 RS4 difference was greater (70bhp) but the character of the RS is SO different to the S - S = soft boulevard cruiser, RS = edgy performance vehicle.

If Audi have retained the same character difference (which is about a lot more than just power - it's about handling and edginess, etc.) between the S5 and the RS5 then I'd still opt for the RS5 - especially as it will have a characterful V8 exhaust note and not a bland V6 exhaust note.