Markakis technically had his best season since 2010. He's a poor defender who didn't hit last year and was just above average this year. I think Aoki is a little safer because you know he's going to be a plus defender (who can play CF in a pinch - aka not Joey Bats) and at least an average bat and should cost less.
Edit: Okay, maybe not as good as a defender then i thought. Still way better then Markakis.