I wouldn't switch if you already have lenses. Chasing picture quality these days just isn't worth it. The truth is that all of these cameras can take some outstanding photos.
However, most people never truly see what they can get because they don't do any post-processing with programs like Aperture, Lightroom or Photoshop. That's where you really draw out the colors and make things pop.
I don't know anything about which Canon does what, but I'm confident that you don't need to switch to Nikon just to get better photos. Lots of Canon photographers can produce outstanding images.