I was going to say Flower since I wasn't familiar with Alexis. But after looking Alexis up, she's pretty damn cute. And yeah, she's got a big, healthy ass too.
Tough choice just on appearance (though I guess Alexis is cuter). But I've seen a lot of Flower's stuff and she's a filthy, nasty girl. I'd need a tape measure to break the tie. And in a tie, the filthy, nasty girl always gets the nod. Give it to Flower Tush.