Main Motorcycle: 2014 Street Triple R
Join Date: Jun 2015
Location: Ann Arbor, MI, USA
IMO, shorter is better for a crash (not a tip over). I've personally seen bad results when a long slider digs in and slams or flips bike. I believe the frame slider is meant to protect the expensive bits (frame, engine) and not all the periphery (lights, etc). Also, the ones that use only one bolt tend to bend. I've seen that many times.
A tech from a national race team personally told me that the Triumph frame sliders crash very well. That was for a Daytona but they're of similar design.
IMO, if you're worried about dropping the bike at very low speed or having it knocked over in the garage, then long ones are probably best. If you go to the track, then wide (span two bolts) and short(er) are best.
To each his own, though. Most people put aesthetics over function anyway.
The Triumph ones are also great for securing the bike into a chock. Very handy place to loop a soft strap.