I had the Turbo for 2 weeks, and the Nexus for the past week. I'm keeping the Nexus with some trepidation because of battery life. Keep in mind that the Turbo might get yet better in that dept once it gets 5.0, while with the N what I'm seeing is what I've got.
The Turbo gave me over 6 SOT with 24 battery life. I'm just about able to get 5 SOT with 14 hours on the N6. I'm not that heavy a user, but wanted to work both phones hard so I'd know how they compare. I don't want to husband battery when I'm out hiking or visiting a big city for the day and away from my chargers, which made me lean strongly towards the Turbo. OTOH, if I'm doing those things, I shouldn't be spending 5 hours looking at a damn phone. And if I did, my wife/kids would be well within their rights to brain me.
In every other regard, the N6 is a phone I love, while the Turbo is one I like "a lot". It depends, of course, on how you'll use the phone. I've generally reserved used my phone as a communication device, and the Turbo is perfect for that. When I want something to entertain myself, like on a plane, I've brought my N7 along. The N6 would serve both of those purposes, provided the battery holds up. Note the circular reasoning: If it wasn't so versatile, I would bring my tablet. Trying to use it instead of my tablet puts me up against the battery limitation. The worst case is that I I'll carry my tablet on a plane like I would if I kept the Turbo. And the N6 should get me out of the house and home on a single charge.
So:
- Size. The Turbo has a generous screen. Until you get the N6 in your hand. Then, it's puny.
- Shape: The Turbo has some rounding, but is predominantly a box. The Nexus' curved back fits my hand shape like a glove. Personal preference, but I simply love holding it.
- Screen size: Using the N6 as a browser is nearly as comfortable as using my N7. I often don't bother finding my tablet if I start browsing on the phone at home. The Turbo works perfectly well as a phone. It's great for browsing, don't get me wrong, but not to the level of the N. I wouldn't want to use it to do more than bide the time waiting for a meeting, etc.
Hope this helps. Feel free to ask me questions. BTW, I'm not much into the cameras, so that didn't even enter my calculation.