I owned both in my Dynasty up until very recently where I moved Markakis as part of a deal. At the time of the trade Markakis had around 30-35 more points than Hart. I looked at the walk column and saw that Markakis had about 30 more walks, which made up for the 30 points disparity (with my league giving a point per walk). I think that if Hart just gets more discipline at the plate to take more pitches, he's just as good as Markakis if not better. I definitely think he has more power and speed. Both are very solid though.
Thanks to soty for this sig