This is a tough one, but I'll stick with what I did and say full sternotomy, for now.
My surgeon told me that he does perform minimally invasive procedures but that it doesn't give good exposure and compromises the operation to a degree. According to the national data, he said there has been double the risk of surgical stroke. The problem had to do with getting all the air out of the heart, which is harder with limited access, and that air can in turn go to the head. This is my translation obviously, so forgive me if I'm a little "off", but from a non medical point of view, that's what I remember.
Now, Cleveland Clinic says minimally invasive sternotomy (6 cm ~ 2 1/2 in) is now standard for aortic valve replacement, they only use a full sternotomy for more difficult cases. They also say that in experienced hands the operative risk is slightly lower.
So, if I were going to Cleveland for example, I'm sure I'd feel more comfortable going minimally invasive, but probably still wouldn't do so unless I had complete confidence from the surgeon that they weren't sacrificing anything using that approach, not even a small percentage of additional risk.