Based on all the cookers I have owned and cooked on, I have often said if I could only have one cooker and budget was a factor, I would have to go with a Weber Kettle every time!
Like Smoke mentioned, you can grill or smoke on them (I've always done a LOT more indirect cooking on our Weber Kettle than actual grilling).
The main learning curve is in using the right amount of charcoal for various types of cooking, then fine tuning the temp using the top vent (close it down to lower temp, open it more to increase temp).
Talk about durability, the porcelain-enamled kettle itself is covered by a ten-year warranty from Weber. Our Weber Kettle is over 27 years old now. It has a few dings, BUT IT STILL WORKS! And... the newer replacement parts still fit even our old model and are easy to find.
As far as versatility goes: there are more accessories available for Weber kettles than any other grill.
Yeah, a 22" Weber kettle get's my vote!