Well for pvp i'd say Nano is definitely the best breed you can have, but i'm a nanomage fan.
As Goat said, we get a pretty absorb from endurance booster, very useful, even while stunned. Saved my ass countless times.
Now people might yell, scream, and do /wrists about the "uber soli perks", but together with hp/nanopool ratio under nbg for nanomages and the fact that they have no problem pulling as much evades as a soli (in ya face), which are still a viable defence, especially if you combine them with blind and/or dazzle with lights (seriously, who doesn't do that?), AND the fact nanomages have less hp in general than soli, nanomages tend to be THE best for a pvp NT.
That was a very long sentence O.o
That was for pvp
For pvm, i think trox actually might be best choice :/ (you're still ugly)
Even tho i know pvm NTs claiming to pull over 15k hp as nanomages, with trox it would be even calmer walk in a park.
As mentioned before, no lvl-locked nano has reqs impossible to be reached by a trox.
Granted, you'll have to wait longer for SL roots and calms, and NR debuffs, but that's not very relevant, is it?