I am black guy and I have fucked with black and whites. From my experience, black guys aren't necessarily better tops, just different. Speaking from experience of one black man fucking with another, the shared race brings a different element to the sex. I feel it is a different "bonding" experience. I will admit black tops can be more rough, dominate, and forceful. I find black men are more apt to want to BB and more into long session that quickies.
White tops, I find tend to be more piggy. If I had the choice to choose, I would choose black.
Sadly, as much as I like white guys, not many white guys are open to black men. I often see "not into blacks" in many profiles.