Kayaker: I really loved my 15-85 on my 50D. It was perfect for nearly everything I wanted to do. I wish I had kept that combo and purchased the 6D as my primary body.

JKP, I was in the same boat as you at one point, and I upgraded to the 7D first, then added a 5D to play around with. I found I liked the IQ better on the 5D, sold both of them and went to the 6D. When I sold the 2 cameras, I also sold 2 lenses (70-200 f4 & 15-85). Then I purchased a 7D again for a project, then traded it in for a Sony A6000. Before I made the switch to FF, I made sure most of my lenses were FF compatible (Tamron/Sigma make EF-S lenses that can be mounted on FF cameras) and good quality. Given what I shoot, I wish I had made the jump to the 6D immediately instead of the 8 months where I had the 7D & 5D simultaneously.

My experiences only......