Which to buy??

i recommend the sony because the sensor is much better than from the 600D, sony produce the best sensors on the market at this time.

The Sony is an amazing camera and since older Minolta lenses will fit onto Sony A-Mount cameras you can pick up amazing used lenses cheap. I don't really think the Canon has any advantage over the Sony. The A65 has it on FPS, image quality, color, built in GPS, more focus points and battery life. The only thing the 600D really has on it is a higher res screen. Sony A65 all the way

It has good low light capabilities, a large and bright viewfinder. Also great when taking video because it has phase detection autofocus compared to contrast detection.

i recommend the sony because the sensor is much better

Sony A65 has biger viewfinder, and better, cus you can see better than your eye, I checked, cus i have an A65, you can shoot at 10fps at 24 MP with continuous focus between shoots !! A65 has a nice HDR  ; A65 is really impresive camera ! and you have image stabilization with all sony, minolta, sigma, tamron lenses !! canon  dont have this greate feature ! 

Sony A65 is amazing !

I am a bit biased but I would recommend the Canon. You have so much more lens choices and some of the faster lenses are cheaper than the Sony counterpart.

If you search for a review of the Sony A77 on DigitalRev, there is  a mention there of the SLT cameras losing a stop or two of light when compared to a normal DSLR because of the fixed translucent mirror. This may be a critical factor to consider when shooting in low light.