I'm trying to decide the same thing so thanks for starting this thread! I think Riu Palace is considered half a star higher than Santa Fe. But I have heard both are good. I'm leaning towards the palace as well, for the same reason you listed above-that guests can use both resorts if you stay at the palace. I heard the santa fe is a bit more lively so at first I wanted to go there because I have quite a few friends that like to 'partay'. After thinking about it, I am wondering if my older guests would like the quieter atmosphere at the palace and us young ones can still go over to santa fe to the bars at night if it is too quiet at the palace. Anyways, good luck with your decision, keep me posted with what you decide!