Tire size need help

Going throw tire sizes and need some help! I want to stay at a 37z for now but dont no what to dump my money into for a size do i go 37x12.50r17 or do i go 37x13.50r17. What im looking for is the pros/cons(if any) and what others have found this might help to limit my tire selection(as in nitto vs. toyo), any help is great thanks guys!!

surface area=traction in dirt dry surfaces or rocks....but being from Boston I would be more concerned with is negative side effects in spring and winter driving which are surface area=skis on snow rain or ice! ultimately it comes down to tread pattern though. A 13.5" tire with a ton of sipping and water clearing channels between lugs will be better than a 12.5" tire with no sipping. There's no blanket "right answer" to this and it all depends on use and the individual tire its self.