Black Ops will sell more on 360 no question.
However, I think Medal of Honor may just sell more on the PS3 for a few reasons..
1. Pre-Orders in America are very close and in the end I don't think there'll be a huge gap in sales there.
2. PS3 owners in Europe/Others are more likely to pick up Medal of Honor because 360 owners already have two big shooters in Black Ops and Halo: Reach.
3. Sony and EA have a strong relationship and I have a feeling Medal of Honor will be pushed as a PS3 title in Europe/Others. For example Sony are releasing brand new gaming headphones in October to coincide with the launch of Medal of Honor.
http://presscentre.sony.eu/content/detail.aspx?ReleaseID=6094&NewsAreaId=2
You get the game free when you buy the headphones. While that alone won't push massive numbers, it shows that Sony and EA have a partnership for Medal of Honor in Europe which will likely determine which version of the game sells more.
