You can drive yourself crazy over these choices (as I have) or take a chance on the wisdom that comes from experience. I'm assuming I have some of the latter......I had a 70D and accidentally bid on and then won a 5D Mark II. (I shoot all the stuff you do...and sometimes blow up to 3'x2' for framing and selling.) After a period of time, having sold my 70D and just using the 5D, I found I missed the great stuff about the 70D and wasn't that impressed with the FF output, i.e. it really wasn't that much of an "improvement" over what I had gotten from the 70D. I sold the 5D and bought another 70D and have never looked back. You'll find a lot of back-and-forth about FF vs crop sensor all over the net, but frankly, unless you're a pro and need output for very large prints and/or do a lot of cropping of small parts of a picture you've taken which you subsequently blow up BIG, you will be hard pressed to find a difference in print quality in the end. As for shooting in low light, well, the 70D has a very nice pop up flash that takes care of that. BUT! After all I've said here I've no doubt many will jump all over this with details about FF that will, supposedly, blow what I'm saying out of the water. If you're taking good pics with what you have, a crop frame camera, there is really no need to move to a heavier and more bulky FF....