I'm a cast iron fanatic when it comes to skillets and indoor cooking, but I really don't want a cast iron grill grate. I'm happy with regular grill grates. I don't want a hinged lid, either. I want a Weber Master Touch but I don't want the lid bale. I'm a weirdo.
I do like the thermometer placement on the Napoleon more than Weber's, as well as the included heat deflector. Those are both nice features, IMO.
If the quality is equal then it really comes down to features and price. I like Weber, but I also like my 14" Old Smokey enough that I probably won't be buying a WSM anytime soon.