Can't speak for the GS500, but the Ninja 500 has been around for a quite some time (mid to late 80s I believe) where the SV has been around since 99. I've owned both the SV and the Ninja 500, go for the SV. It's just an all around better bike. More power, better handling, low fuel light, fuel injection (2nd gen). I'm 5' 8" and can fit on the SV pretty well. I think the SV will be able to handle two up riding better than the Ninja but can't speak from experience.