NEX 6? Any downsides?

Talk about BS. There are, as I said, next to no NEX lenses actually available. The few lenses you listed were mostly "available some day but not today" or duplicates. It's great that there are nice plans, but you can't take photos with plans or announced intentions. According to B&H there are 11 including duplicates and near duplicates. The variety of shooting situations covered is very low. The only thing it competes well with is the even newer mirrorless systems. Let see, 1 macro at a useless FL (no working distance), 3 short fast lenses, 2 short f2.8, a JOT 18-200, a slow telezoom 55-210, and a pair of slow standard zooms. Not much selection. Not many shooting options covered.

As for Nikon DX, more BS. There is no such thing as a DX mount. There is an F mount. DX only means that the image circle is not large enough to cover a FX sensor. There are over 150 (last time I checked) F mount lenses. A DX body can mount all but 2-3 50+ year old ones (called invasive fisheyes). Since you brought up the F-mount and decided to lie about it, lets compare. There are nearly as more F mount 50mm lenses (20+) then there are NEX lenses  so you can get exactly the type of lenses your shooting and budget demands.

A partial list just off the top of my head.

50 1.8d, 50 1.8g, 50 1.4d, 50 2, 50 2.8, 50 1.4g, 58 1.2, 50 1.2, 55mm macro (3-4 versions), older 50mm primes (5-6 versions incl AF, AI, etc), Sigma 50 1.4, Sigma 50 2.8 macro, Zeiss 50 1.4, Zeiss 55 1.4, Voigtländer 58 1.4, and so on (not a complete list). These are all "DX" and "FX"as there is no such thing as a DX mount.

Fast glass (f/2 or faster) is available on 20, 24, 28, 30, 35, 50, 60, 85, 105, 135, 200 and 300. Again probably not complete. And all "DX" or FX.

F2.8 lenses? Evern a longer list.

Telephotos with actual reach (not just 200mm), over a dozen (maybe several dozen). I think the longest is 1700mm. The longest easily available is 800mm.

Wide angle, including fast wide angles, over a dozen.

In every single possible category the Nikon DX camera user has more choices then the entire rather small NEX lineup. And you will note I did not include announced but not shipping BS to try to create a false impression like someone else.

Trumpting that the very small selection of NEX is in any way comparible to what a DX user can use was just funny. Stupid, but funny.

--
See my plan (in my profile) for what I shoot with. See my gallery for images I find amusing.