255s are taller most guys like the taller tire for more mph it lowers the rpm on the power band ,235s are like 26'' tall and the 255s are close to 28 '' tall.
I always say the more tire you have on the ground the more traction , but the 235s will hook good also and look more stock on the GN wheels i run 235s all around on my GN wheels but run radials , I run 275/60/15 DRs on my Centerlines.