msslaveGood point. It really depends on what the disposition of the "sucker" and the "suckee" are.

If the "suckee" is submissive, it's a lot more likely that the "sucker" can or will take a dominant role and vice versa.
Those who are versatile in their roles, can be (and do) both.
I permisterally find it a huge turn on to see someone aggressively sucking cock, like they "own" the suckee and he's just a toy for their amusement or a badge for his/her sucking prowess.
Wannabe - see my captions at http://www.cuckoldplace.com/27_74912_1.html