Kettles are awesome! I did my standing rib roast in my 18 WSM because it is the easiest to control to about 225°. As it neared the desired IT, I fired up a kettle with a full chimney of lump for a sear to finish it. After the roast was seared, I closed it up to save the rest of the lump. The next day I relit the lump in the kettle and set the vents for about 275° and put a couple hours on the ribs trimmed from the roast before serving. They were great!
Can't beat the WSM for low 'n slow cooks but overall, the kettle is the one capable of doing it all!