Already a lot of good advice. As someone who jumped from the 7D to 5DIII, I just want to add a few thoughts:
  • At least for me the jump felt like more of an incremental improvement in several areas. The IQ from the 5DIII is better, especially low light, highlights, transition between areas of contrast, and bokeh. But in terms of "what can I take" that I couldn't take before, do not underestimate how good the 7D is and the fact that the 7DII and 80D (maybe even T6i) will have better IQ than the 7D. I think you will notice the improvements right away, but the
  • Lens selection. I just want to echo what someone else said and more lenses were intended and designed for FF compared to APS-C. This is great, but, if you start buying those lenses, it is not cheap.
  • Along these lines, APS-C seems built for utility. I had a wide range covered with my 7D, EFS 15-85, and 100-400 L. Slower glass, sure, but for travel, walking around, and just taking pictures, amazing. Because of the larger image circle, FF does not have an equivalent to the 15-85. To have faster glass covering the same range I find myself with more lenses. Which, in the end cost me more, and has made traveling a bit more cumbersome.


I don't want you to misconstrue my intent, there are advantages to full frame. I would just think about what you want, what you need, and why you want to make the jump. APS-C is very capable and actually has a few advantages, particularly, convenience.