It depends on your goals.
If you want to pursue a career in academics, then you'll be better suited to train somewhere that produces academicians.
If you are wedded to a specific geographic area after graduation, then training in that area will help you by availing you to a network of connections.
On the other hand, if what you want is to become boarded in HPM so that you can practice good HPM, I think it's going to be mostly about "fit", which is an admittedly ambiguous term. I do think a good mix of clinical experience is important - you want to treat not just patients with advanced cancer, but also heart failure, stroke, dementia, COPD, etc. So asking about case mix is worthwhile. But if I had only 2 questions to ask of a program, they would be:
1 - What are your recent fellows doing now?
2 - To the current fellows, are you happy?
