Pete: Your question is like asking what flavor ice cream one likes. There are a million opinions on this subject, but I'll give you mine since you asked.
As a collector who shoots occasionally, rather than a shooter who occasionally collects, I tend towards the view that the older, high quality target revolvers like the OMM should be respected, shot within their intended limits and preserved, rather than pushed to the max unnecessarily. Can one shoot +P loads in the OMM safely? I would guess yes. Would I do it in my own gun and run even a small risk of damage to a quality gun that will never be made again? No.
If you want to shoot +P loads I would say shoot them in a revolver that was originally designed to do so, and save the OMM for target loads.