Hogloff wrote in post #17924666
Depending on how you shoot...that pocket full of batteries is an exaggeration. I typically carry 2 spare batteries and only once did I have to change to one of the spares...never had to use a 2nd spare. I get roughly 400 photos per battery and typically don't come close to shooting 400 photos in an outing. The only time I has to change batteries was shooting a music concert.
I usually don't even bother carrying a spare anymore... I used to carry two because of all the fear spreading here on the forums, then realized I never needed them. True, if out on a long day you'll probably need one more, or if you leave your camera on all the time like you would a DSLR then you will need more, but shooting normally a whole day on my a7S one battery is almost always enough.
As for the OP; If the top 2 reasons are your main ones for wanting the a7ii, I'd stick with the 6D...
More megapixels is irrelevant in my opinion... I went from 20, to 36 and now down to 12, from a practical standpoint it made zero difference to the quality of the shots I'm getting, and 4 megapixels is as near as makes no difference.
As for picture quality... yeah, it's better at low ISO, how much so really depends on who you ask, but if you ask me, it's again a wash (having owned a 6D). The DR advantage can be handy sometimes, but it's not something to switch systems over in my opinion. I made a before and after sample with my 6D that I constantly used to defend it's DR and switching to Sony hasn't changed that perspective/argument, the 6D's DR is fine. As for ISO performance... you'll be disappointed, the 6D is better in this regard from all that I've read/seen. I had the a7R right after my 6D and was astounded at how much worse it's high ISO ability was coming from the 6D, so much so that I sold it for the a7S (because I loved the ergonomics) and most people agree that the a7R files are actually easier to work with in regards to high-ISO than the a7/ii files are.
If the other points you brought up are more important to you (minus the WiFi, since the 6D also has that) than by all means, get the a7ii. I'm a huge fan of mirrorless for all of those reasons (and a few more).
Another thing you may want to try is to get an EG-S screen for your 6D, in my experience it makes manual focusing much easier with fast glass.