I think the biggest thing is more what sort of research project are they going to push you towards. And what sort of apparatus do they have in place to get you there.
Everyone graduating from a PCCM program is expected to be able to run a code, manage critically ill patients, be procedurally sound. That sort of discrepancy in training in the basics is long, long gone. Maybe you'll get a better or worse cardiac experience, variable volumes in ECMO runs, and more or less neurocritical care specific training, but the rest should all be there in spades.
You want to make sure though that a program is going to push you through a project at a fellow level, is going to help you build some sort of niche, and hopefully put you in a situation that when you interview you can explain a roadmap to tenure, ideally with some sort of thought on where you might garner extramural funding. What you don't want is people who are going to let you get by with any sort of old project. I'm in a private practice group with no academic demands and we have passed quickly on candidates due to their research project...it's a kiss of death if people are asking how you got away with a project that is more in line with a medical student than a fellow. It raises questions about your ability to think critically and adapt to novel situations if you can't see that your project is limited in scope, impact, and execution.