I have a t2I. I've always been very happy with it, but I would like to buy a new camera. Basically so I don't have to switch lenses as much. I shoot pretty much anything. Mainly wildlife, nature scenes, and old buildings. I thought if I'm buying a new camera maybe go for the 5dmrk2. I worry about losing reach on my wildlife pics. Would I really lose reach or can I just crop all the way down to what I would get with my t2I?
As far as lenses go, I have a canon 24-70 2.8, 100-400L, 10-22, and 100 2.8 macro. I think if I go with the 5dmrk2 my 24/70 would be great, but id also have to find an equivalent ultra wide angle. Are the low light capabilities of the 5d2 really worth me adding that camera, keeping in mind I still plan on carrying my t2I on my hikes?
I'd say the main thing you need to consider is which aspct of your photography your looking to improve.
The 5D2 probabley would not help you much for shooting wildlife unless you can get very close where as it would improve IQ for closer subjects and in low light.
If you wanted up improve that aspect perhaps consider the 7D or 1D3 used? you'dnot gain any resolution but would gainy improved AF and FPS.