The most important difference you will notice is the improvement in sound quality with a high-end mixer. All the FX and/or extra channels are nice.... but the sound quality is always my 1st consideration.
The new Pioneer mixer lineup has made nice advances in the sound quality. I think this will probably be one of the things you would notice first. Once you get used to playing on a good mixer, it will be hard to go back. I refuse to DJ on anything but an Allen & Heath mixer, personally. If the club doesn't have one, then I bring my own.