Depends on the shop. I'd generally believe that there's going to be the potential a human factor in both. I'd choose the shop route, go with a shop you're confident with, and involve yourself in the process as much as the shop will allow. If they know you're invested in the build, they will naturally take a little more care in it than a motor that was just dropped off & picked up a month later. ..... This one could be a real can of worms.