I have both and I use the WSM primarily when I need smoking capacity. I use the egg to sear steaks and cook chickens and roasts. The egg can be brought to 700-800 degrees in a short period of time and cooks the best steaks I've had. The WSM is a great smoker for the price and cooks great meat.
BTW, if you're spitting rocks out of your mower that will break the egg, you've got bigger issues. Hope you don't have kids.
LBGE, 22.5 WSM, 14.5 WSM, Weber 26.75 OTG, Weber Performer, Backwoods chubby, Speed of light fast Packer green Thermapen, Speed of sound fast red backlit Thermapen, Ultra-fast American flag Thermapen