First off I believe you can almost do the same with one as you can the other. However, controlling temps on the Weber would likely be the challenge versus the BGE.
I have both and view one as a grill and the other as an oven. If the Weber Kettle did the same as the BGE then there would likely be no need for the Weber bullet smoker.
The Weber I have is a monster Ranch model grill (shown below) and works well as such. But temps are difficult to maintain for more than grilling steaks and chicken. Never tried a low and slow for butts on the Rancher but I might just do so this weekend and report back.
BTW the little ole Smokey Joe is my favorite all-purpose grill!!! And it fits in the trunk for tail gating.