OMG BUY CANON!
With SLR's it all comes down to lenses. If you invest in the quality lenses from Canon, Nikon, Sony, etc you will get better results. Saying that, sticking with canon or nikon helps as they are more the pro series so there is more choice and reviews and the like out there.
Have a look at what you will be doing, there is no point buying a fully siq body and then using cheap lenses. Better to buy a cheaper body and the best lenses.
Then you can also look into whether you want a crop body or full frame... etc etc etc. Cameras are worse than cars!