I think the direction of this theme is on track: to wit we cannot know how average or how awesome the MOM implant is until we have medium to long range track records and a study group of similar quality (device type, cup angle, abnormalities, age, activity level, etc.). Unless you compare apples to apples things always get murky.
I think too, that the activity and stress put on most THRs is probably less (maybe a lot less) than with HR patients. Lets be honest, that's why most got them in the first place - to be more active. As Dr. Gross stated somewhat enthusiastically during my 6 weeks appointment (I paraphrase): "If other hip doctors could see what most of my patients can do with an HR they wouldn't believe it".
It is my sincere hope that most of us here will be excellent long-term data for the longevity of our implants, regardless of the type. Selfishly, I'm pulling for mine a little harder than most - my bad!
Curt