Hi Lee, I've been running Gens Ace and Turnigy 3S 5000 25C lipo's in my Hex for about 7 months for a comparison and so far in terms of performance they are pretty well identical. There are 2 GA's and 1 Turnigy and they have over 70 charge cycles so far and flight times between the batteries has stayed consistently at just over ten minutes before the battery alarm goes off. I originally charged them at 1A and now I charge them all at 5A for the last 30 cycles and I've seen no drop in performance. The biggest difference is in the price, the Turnigy was half the price of the GA's.
I have a same spec Turnigy Nano Tech on the way to do a comparison along side the others just out of curiosity, and with the results so far I would have no problem recommending the Turnigy's to anyone.