I upgraded from the 5D to the 5Dii only a couple of months before the 5Diii came out. While I've enjoyed the newer version, I'm not totally happy with it either. So am getting that 'itch' again.
Not real happy with low light, and hate the auto focus.
The 5Diii auto focus is a big plus, but that extra weight and cost is a big down.
The 6D (I've never touched) sounds good and is much lighter than the 5Diii, but the auto focus doesn't sound much better than what I have.
75% of my shooting is when I'm traveling and carrying my camera all day, so that's where weight comes into play. I'm not getting any younger.
Of that 75% almost half of that is low light shots with the other half just being candid street shots.
The other 25% is shooting wildlife. Again it's for hours on end, but most of the time from a car or on a tripod so the weight isn't so much of an issue.
99% of my shots are with available light only.
Don't give a darn about GPS, wifi could be handy, but you don't miss something you never had.
Back when I first upgraded to the 5D I kept my old body as a back up. However quickly figured out that traveling with 2 bodies wasn't for me. Just too much to pack in that carry on bag on the plane. So I'm trying to figure out which one body will serve me best.
Of course price is a factor, however if one is not happy with their gear cheaper can cost more than money.
Would love to hear some thoughts of the pros and cons and suggestions. Am I'm being to picky or would one of the other cameras serve me better.