For me, there are a few things I consider before making the final cuts. I always make a test cut (or two, or three) with two, 12" long pieces to see how a straight-forward miter is going to work. I use a Bosch miter finder these days, so getting an accurate cut is simple. If it looks like the miter is going to work, I go that way. If there are undulations in the ceiling or wall close to the corner, I may go with coping. I consider if it's stained or painted molding as I can cheat a little with painted (read: caulk). I only do crown a few times a year but must say that I end up coping most of my inside joints. Just seems like a better and tighter fit.