I don't know why you prefer Aperture, but I have the opposite feeling.
I love Apple and it's apps, but lightroom is to me so much more pleasant in its user interface, its layout and it just looks so much more appealing to the eye when working in LR! I have ni idea which one makes better prints, but on screen LR is a winner to me.
That said, I do miss aa few things in LR, like a spot healing brush and a good sharping tool...
And btw, I looovvvve the option of a managed library (which they offer both). I have allways struggled with multiple folders and backups taking far too much space and being inconsistent in the way I keep my files. Now this is alll over and done for me!