Pretty much what Danny said.
I went to two surgeons who promoted only THR and advised against HR when I brought it up. This was at two of the more prestigious medical centers in Boston.
They said that at one point they did HR, but no more because of the metal ion problems. That is a valid concern, for those of us who develop it, but it is a small part of the results of an HR procedure.
What they also didn't mention was that the results from HR were equivalent in the short term to THR and I believe in the long term, better for active people.
They were also talking about traditional THRs, not large head THRs. They mentioned all of the things I would not be able to do, which sealed the deal for me. They were older and probably more practiced in doing THRs (my own editorializing).
I found my doctor after that. He looked me over and said I was a perfect candidate for HR. My thoughts were then and now, that after looking at the statistics, the results, etc. I still felt in my gut that preserving as much bone stock as possible and keeping the device to as small a body footprint as you can is the right way to go when it is possible
THR is a great alternative, I think when an HR is not possible. We have some great and active hippies with THRs who are living their lives joyfully. An HR does require more skill from the surgeon not just in the operation itself, but in selecting the patients, addressing any conditions that need to be ameliorated before doing the procedure.
So it's more work, and in the corporate health care monoliths that we deal with now, that kind of extra attention may not appeal when you can address the same condition with something both more expedient and that more surgeons with less training can do. (Again, my editorializing).
It's why one of the measures of success is finding a good surgeon. Not just skilled, but well practiced and with at least a couple of hundred procedures under their belt.
Just my opinion. I am closing in on three years on my hips and am thrilled with the results.