I'm not 100% sure of the technological differences themselves (I think it's just a standard LED compared to a laser diode) , but laser mice usually have a much larger DPI, which means better accuracy.
Also, in my experience, laser mice don't get any of the whizz-off-to-the-corners or "crawling" that optical mice almost always have.
Tbf, my experience with optical is limited, since I moved straight from ball -> good quality laser, but every optical mouse I've used on someone else's machine has always had the whizz-off or crawl effects, regardless of the price of the mouse or the surface used (yes, even single-colour high quality mouse pads).