Why take a year off before applying?
If you're willing to lose a year, wait to see if you don't match and then do a research year if you don't.
I thought about taking time off for research because I wasn't super confident in my application. I was hoping for 3-5 interviews, but got more than a dozen and matched at top choice.
I've also heard of people postponing graduation after the match, doing a research year, and re-applying as a senior medical student and matching. In my opinion, I don't think that makes a huge difference.