Going to use camera to mainly take pictures of wildlife and sport

I currently own a Canon 60D so I can tell you more of what it can and cannot do.  First off, both camera are quite the same when it comes to image quality (if you test them using the same lenses, on tripod).

However, 7D has more advantage in these areas:

- Higher frame rate (8fps on 7D vs 5.6 fps on 60D)

- Faster autofocus (7D has 19 cross type focus points) which plays heavily into your accuracy of auto focus.

- Weather seal: 7D has this, it helps against some rain, but don't even attempt if a monsoon is pouring down on you.

- 7D has dual image processing chips (only helps in photo, not video).

Canon 7D is marketed toward sport, wildlife shooters so it is definitely having a lot more appeal to you, thus the price is higher for this reason.  7D will focus faster, and shoot more photos per second, this means you will have more usable shots.  Your existing 70-300mm lens will play nicely with it.  But if you don't have IS, shooting near 300mm you do need a tripod.

The 60D and 7D are very similar in image quality.  I asked you about your lenses because I was about to suggest picking up a used 5D Mark II... but you already have the 70 - 300mm and I'm guessing you'd miss the extra reach if you went to a full frame camera (300mm on a 5D would only look like 185mm does on a 450D).

The 7D can shoot more frames per second and has significantly shorter shutter lag.  So on those few points I'd say the 7D.  (But if 300mm isn't too important then also consider a 5D Mark II, which has better image quality and can go higher in ISO)

7D is geared towards sport and wildlife photography with more robust build, faster frame rate and better weather sealing. It's Canon's best crop (1.6X) sensor camera. It suits your stated needs better and can use all your existing EF/EF-S lenses.  For your purpose, their is no advantage to upgrading to 5D MkII/Mk III.