[G]

There is a fair bit of differance physically between the RR5/6 and RR7/8 both have a fuel guage and neither have a gear indicator though lol

I think the RR7/RR8 frame and engine are even completely different from the RR5/6, but I dont know the fine details.

Both amazing bikes though, if you can afford the RR7/8 then obviously get the newer model, as the newer model will always be an improvement over an older model even if its fractional.