A grill is a grill, and a smoker is a smoker. Two different tool for a similar, yet different job. Can you drag race a dump truck? Sure, but a funny car will do it better.
There is nothing wrong with making ribs and smoking a butt on a
Weber kettle. Many guys do. I did for years. But a
WSM does it better, easier, more efficently.
Can you do a stake on a
WSM? what a about crispy skin chicken? Sure, but it is easier on a grill.
See the point? Also don't forget about "Jack of all trades, master of none" when looking a combo units that say they can do both.
IF I was just starting out / over, I would by a
weber kettle grill. Heck, I'd buy the performer if I had the space. Use it, learn it, love it. Make beautiful food together. Do so 'Q on it. In a few years when the family is demanding you 'Q something up for every holiday gathering, then get the
WSM, and don't fool around - just by the big one.
Somewhere in there you will end up with a rotisserie too.....