I haven't seen any benches of the 651, but you can compare the A8 3850 to a phenom ii to get a good idea of the performance.http://www.anandtech.com/bench/Product/399?vs=88
From all the benchmarks I've seen on llanos, they look to be basically even with a phenom ii at the same clocks. Phenom iis seem to get a little bit better performance in games though (a few fps).
I'd say that the only major differences between the two is the choice of motherboards, and that the 960t will be easier to overclock. Also, with the 960 you have a shot at unlocking extra cores.
Overclocking on llano depends a lot on the motherboard, 4.3-4.5 is possible but I wouldn't believe it till I see it.