Why not both?

You wake up Batgirl and have both of the women come out of their cells and have them undress in front of you. Batgirl seems to have a pair of B cup breasts while Poison Ivy has D cup, but both of them are still beautiful. You decide to try Batgirl first, and have her lay doggy style while you have Ivy touching herself. You get up and test the waters, thrusting yourself in, and using her breasts as handle bars. You notice how tight and wet she is. You decided to switch it up though and have Ivy in the same position while Batgirl fingered herself. While Ivy's breasts work better for handles, she's looser. You flip her over fucking her on her back and find that a lot more exciting then doggy style. You do this until you're about to cum at which point you have both girls come over to you and suck your cock at the same time, having one suck on your balls with the other on your shaft, until you cum on both of their faces.