Definitely not GRU. BA is great, but you have to check Rio off of your list. If you are going all that way, why not hit both? Get an award ticket into EZE or GIG, buy a flight between the two, and fly home from the other. They are both very worthwhile destinations. To/From SFO, I do not think IAD or ORD really make too much of a difference. I would try and see if you can get three-class equipment to/from IAD/ORD - SFO and go with that routing.