I would think the reason for doing it in Abottabad would be the plausibility of the whole scenario. ANything else, the contracdictions would have been enormous.

Lets imagine OBL was eliminated in Afghanistan, how do you explain his presence there, where did he get his food, medical supplies for all those years.

With the US presence in Afghanistan you can at best argue for a few sneakthroughs that supported OBL.

So I would say US picked the best case scenario based on circumstance.