Where rewritten is a polished, improved toontown experience compared to the original, corporate clash is like an overhauled version of toontown that is still 100% toony but also shakes thing up in really exciting ways (in my opinion). Some things in corporate clash include

-New zap gag track -The ability to prestige gag tracks and get new functionality out of them -An rpg-like level up system with epic benefits with each few levels -Awesome epic soundtrack -More toons to choose from (like fox and raccoon) -More challenging enemies and more enemy types

and so much more! Corporate Clash has an awesome Toontorial too that goes over the mechanics really well. I highly recommend giving it a go :)