Always better looking job with parts off,pros : no paint edges, no time wasted cutting in, more manageable project best looking job in long run. Cons: very difficult spraying AD truck especially rear fenders to bedsides and getting slick job no runs, difficult keeping wet edge as well. Parts off will require extensive time pre fitting to ensure smooth fit up of painted parts. Parts off will require sufficient amount of paint up front to ensure completion without running out(I wouldn't count on paint jobber to mix same color twice), Metallic color Will require consistent air pressure and gun distance on parts off as well. Hope this helps ,Pat66