Note 2. I have one and love it. Nexus 4 is nice, but in my opinion it just doesn't compare.

XT is a Dual Carrier network - but it all comes down to what you're doing on your phone. DC HSDPA is faster but you won't notice it if you're just doing Facebook, Twitter or light tasks on your phone. Personally, I don't think you'll notice much difference between the Note 2 and the DC version in real world tests unless if you're doing speedtests.

The Nexus 4 is extremely good and was one of my more favourable phones I have owned. Again, comes down to what you're wanting to do, both are excellent devices, might be worth even looking at the Galaxy S4 since for you it ticks all boxes and as-long as you don't liquid damage it then it's futureproofing you a bit more.