resurfacing doesnt do harm to your ball unless you resurface it that much that it gets too small and the ball return cant grip it and it wont return. resurfacing is the only way i know off to get rid of those scratches and duts in the bowling ball surface and also(some1 correct me if im wrong) takes some of the oil out of the ball. This is a good thing while only removing i think its like half a millimeter of the balls surface. The only reason you would want to repolish your ball is if it was polished in the first place or you feel that your ball is hooking too much and you need it to go down the lane longer before hooking, if this is not the case i recommend that you get it sanded to 800 grit