I use a pair of 7Ds alongside a 5DII.
Personally I wouldn't consider it an upgrade, going from 7D to 6D.
Unless you are making really big prints, you aren't going to see any noticeable difference in your images. Unless you are shooting a lot in very low light, the 6D doesn't have a lot of advantage over a 7D. It falls short in a number of other ways. Likewise, the 24-105 falls short of the 15-85 in some ways, too.
You can use an ST-E2 or ST-E3 module to control off-camera flash, if you wish, instead of getting another flash. In fact, you might even want to consider that for your 7D. It's superior to the in-camera wireless flash control on the 7D... The ST-Ex use near IR light to communicate instead of obnoxious white light flashes... And with continuous use they don't overheat and shut down. On the other hand, the new radio based off-camera flash control system is immensely superior to the line-of-sight-limited optical based system of the earlier flashes, control modules and cameras... Maybe it's time to start converting to that? (Rumor is a radio-controlled 430EXish model will be coming soon, to complement the 600EX-RT.)
As someone noted, you will need to replace 3 out of 4 of your lenses. For full frame you have a bit less choice of lenses, than you do with crop cameras. And a kit of lenses for FF will tend to be larger, heavier and more expensive.
Frankly, your best bet would be to buy better/different glass to use on your 7D... Most of which doesn't have to be "crop only" and might put you in a better position to switch to or add a FF camera in the future. Get some larger aperture primes and you'll have a lot more opportunity to blur down backgrounds, control DOF.
Oh, and yes, the 7D will drop in value when a new model comes out. But 6D will start to depreciate too, as soon as you remove it from the box and take a shot with it.
I believe there are geotagging modules you can use with your 7D or other models. Personally I'd rather add a module like that, than have the feature built into a camera.
StillCrazy wrote in post #15668130
Thanks for this. I too am trying to decide, 7D, 7Dii, 70D, or FF. I shared many of your comparison thoughts, but I didn't have confidence in my own reasoning. Now I feel better about not going FF.
I'm a serious hobbyist, not a pro. The expense of changing formats is way to high to justify it. If I can get good results with the 7D series, than it makes more sense. I don't need the high fps rate for sport shots, but it will not self destruct if I use it only for portraits and landscapes.
StillCrazy, your signature shows a T3i, not a 7D. However, based upon your described uses, a 7D isn't going to do much for you and a T3i should be fine. Essentially they use the same sensor and give the same image qualities. Same with a 60D.
A 7DII and other "next-generation" Canon APS-C are likely to be around 24MP cameras, just based upon what the competition is doing. That may or may not be a good thing, may or may not be "upgrades", depending upon how the future croppers handle noise at higher ISOs.
