Another opinion FWIW:
I'm building another +4 right now. We've run stock, +2 and +4 on our very tight trails and the +4 is the quickest. Our mudlites really hook up in our terrain and an aggressive rider needs to keep the front tires planted to turn. The shorter arms want to push the front off the track accelerating out of turns.
Depends on where and how you ride. Also depends on your size. If you're small, a short arm is OK cuz your weight will be forward ... if you're 6'4" , 260lbs with long legs & arms your ass will be by the grab bar and ya wheelie at the touch of the throttle