I visited Nimes in April 2012. I went shortly after Arles and I must say that I very much preferred Nimes overall! There was a reenactment when I was there and the Roman arena was packed and really impressive. The view from the Tour Magne was quite worth it too. I decided to stay overnight and I wasn't disappointed. Should I be in the vicinity, I would gladly revisit Nimes over Arles anytime.