We're having the same dilemma, so if you figure it out I'd love to know! :) (In our case, two of our three doors are actually pullouts---DH wants the lone door to have its handle at the edge, while the other two are centered, but I'm thinking this will look a little silly, especially given that the one door is half of a pair where the other is a pullout...)

Are your cabinets slab or shaker? We've also been struggling with whether to put the pulls on the rails for the doors/large drawers, or in the middle of the center panel like the smaller drawers. That might make a difference on how you center them horizontally, too.

We have slab base cabinets and only a very few uppers that will be frames with glass fronts. I am leaning toward all the pulls near the edge (where they would be if there was a top rail) on on the bottom rail for the uppers. I am leaning toward the center for all since most will be drawers or pull outs and only a few drawers. I think, for me, it is going to bug me to have some on the "corner" for doors and the rest in the middle/top for drawers and pull outs. I think they'll still be easy enough to open and they'll all look the same.