The Easton Nano is a pure carbon arrow with some sort of nano tube technology. The FMJ is an aluminum wrapped carbon.
You cant go wrong either way. I use the Nano's and love them. I originally wanted to go with the FMJ's but they were a bit heavier and I thought they would slow my bow down a little bit more then I wanted, so I went with the Nanos.
Both arrows are super tough, and penetrate extremely well.