You can put a nifty 50 on a 6D and you won't even feel it, you can carry it everywhere you go. The 24-70 2.8 ii is also lighter than the previous 24-70 I used to have. It's light on landscape shoots while on the tripod over my shoulder. I wish I would have never sold it, however I'm finding I like the 6D more in a lot of ways, lighter, the ISO seems to be a hair better, the wifi tethering on photoshoots, I shoot raw, but I get a full size jpeg preview on my iPad pro which has a 13 inch screen without using USB extension cables and pulling out a macbook. I ended up testing a friends 5d Mark iii against my 6D and could clearly see it wasn't worth getting another 5D Mark iii. I thought it was a big deal and the internet had hyped it up and I was convinced I needed to go ahead and buy another 5D Mark iii. The focusing points are nice to have, but it's not as big of a deal as you might think. But I'd rather have one card slot and have a new camera. When I had the 5D Mark iii I hardly ever kept the other card in there. We shot weddings, music videos, indie films, etc with the 5D Mark ii before the 5D mark iii came out. Even the 5D Mark ii didn't have two card slots. Two card slots is nice, but that's something new really. Of course I'm using a sharp lens as well. When I can, it's still really razor sharp. Focus and recompose isn't an issue for portraits, anything past 50mm, even at 2.8 I've done test of focusing and recomposing vs having the focus point right on the subject and even at 1:1 I can barely tell a difference, usually I can't tell a difference. I have owned the 5D Mark iii and 6D, the 6D is lighter, the focus point seems way faster, especially if you got a good lens. But it's also possible it does, which is why Canon does their test and puts their number on there. It's even possible the shutter doesn't fail 10 years from now. I take pictures a good bit and my shutter count doesn't go up each year as much as I thought it would in my head. Because of this, he gets cameras very cheap because he doesn't care what the shutter count is. He claims that his test show the shutter can go way over the estimation and usually does.

I have a friend who works in research for camera technology.

Shutter count canon 5d mark iii online