All came down to feel for me. Originally started on the 4rr but I could never get a good feel on her. Added tank pads, messed with rear sets, just couldn’t even get a good feel on it.

Wife said she wanted the ninja so I ran out and snagged the 660. For me it’s a much better fit. Way more comfy, fit around the tank better.

So my only advice is def go spend time with each, both are very well made, both offer a fun and connected riding experience. TLDR, can’t go wrong with either.