For what it is worth, I went through the same decision a few months back. I decided on the NX8, and my logic is as follows (my pricing is a few months old):
DX6e, $200, and uses 4 AA batteries. Nice price, but I did not want to mess with the batteries. Adding a 2000 mAH Li Ion battery and charger runs about $55 in parts... so this becomes a $255 radio.
NX6: $310, with a 2000 mAh Li Ion battery, plus a diversity antenna
NX8: $350, same Li Ion battery. Not a whole lot more $ for two more channels. My vote.

Also, the NX6 and -8 have room for the larger 6000 mAH battery, should flight time require the endurance.

Again, my logic might not be correct, and there are many ways to skin the cat. Ultimately I decided I will probably only have one or two transmitters, and decided to go for a more expensive model.