The Big Green Egg can do what a Weber Smokey Mountain can do, but the Weber Smokey Mountain can't do what the Big Green Egg does (obviously capacity will be different between the 2)
BGE can do high temp searing, pizza's, breads, as well as low and slow bbqing. The thing with the BGE is there are other Kamado Style Cookers that can do the same thing as the BGE but priced lower.
What about going with a lower priced kamado cooker such as the Kamado Joe or the Visions Kamado and also picking up a Weber Smokey Mountain? ManCaveMeals on youtube has great reviews on the Kamado Joe, Big Kamado Joe, and Chargrill Akron steel kamado)
*Weber Mini WSM* *Weber Touch and Go Performer X3* *Sublime Smoke UDS* *Maverick ET-732 * World's Fastest Blue Thermapen **Pitmaster IQ110*