Mark,
I had the same thoughts until...
I have my WSM 14 and my Master Touch 22 in kettle, and there is about one day every two weeks were I wish I had a gasser for a quick fire up. I use my WSM for everything low and slow, and my Master Touch for everything hot and fast and ever hottish and fastish. I have never done low and slow on the kettle, I have never go longer then the hour plus dull chicken need. I have never tried to maintain a specific temp in the kettle over a longish period of time in the kettle like I do in the WSM. I didn't think this was at all a problem
until... This Thanksgiving
With my WSM only being the 14, I wasn't sure I could fit a whole bird in it, but with not knowing how to heep a 2 to 4 hour cook going at 325 to 350 on the kettle (because I have never done it), I didn't feel like that was an option either. But then since I have got my Master Touch I have not cooked any poultry on the WSM so I felt a little unprepared and out of touch to cook a turkey on it. I cooked a whole chicken about once monthly, I did them all the time the WSM until I got my Master Touch and since all whole chicken are done on the kettle.
I ended up cooking a 7 lb bone in breast on the WSM and had a hell of a time getting it to the temp I wanted, this site and enough practice with the cooker had me make changes quickly that make it turn out perfect in the end, but my first plan was not right to get it to the temp I needed. I also cooked a 20 lb whole turkey in the over, because I was not comfortable doing it on the kettle.
So my goal for the next year is to keep using the WSM 14 and the Master Touch in their sweet spots most times, but every once and I while I am going to push both cookers into outer limits of what they can do so that I have more flexibility on what I can cook comfortably on both great cooking machines!