You'll find that the camera body affects the image very little given the 2 camera bodies are within the same generations, the lens plays a much bigger part. You ll find a lot of the sensors going from an entry level dslr to a mid level one are actually the same and the only different between them are usually ergonomics, environmental sealings and added functionality.
It's much cheaper for companies to produce a set of sensors and distribute it throughout it's line up with different levels of functionality than creating a bespoke sensor for each model. Think car manufacturers that uses the same engine in a variety of different models and trim levels, this is the same principle.
One of my all time favourite photographer uses a Canon Rebel XTI (400D) with kit lens and a 50mm 1.8, he does however have to compliment it with, a great lighting system that he uses to great effect. It just goes to prove that a lot of the time the photographer is the weakest link in the system.
