I think GK107 is great and GK106 not terrible either.
Of course AMD does well too. They both do efficient GPU and there's not much flame material unless you want to nitpick here and there.
I think we can order the low-midrange products this way and that it's true for both power use and performance :
GTX 650 < 7770 < GTX 650 ti < 7850
If a vendor sucked and the other not we'd see a card both more power hungry and slower than the competition, as could happen in the past.
( I happen to think the GTX 650 and 650ti are appealingly power efficient
)