Totally depends on the riding and rides you do.. My local hill is a pretty mild 2500' climb for your descents.. The 38t was fine since it was a fire road grinder.. Any flat XC rides were also fine.. But on long epic rides with lots of climbs, I dropped back down to a 34t. Especially since the epic rides were mostly pitchy rolling trail climbs where you couldnt get into a pedaling rhythm.