i would suggest forgeting about what cooker to buy...for now.
you're considering investing 1,2,3 thousand dollars on a tool for something you haven't tried yet.
my opinion, take it for what it's worth, is:
1)get yourself a 22" WSM and a kettle, some blues hog and smoking guns hot.
2)do a practice run or two right quick and HIT UP A COMP! "pro" division, not back yard.
3)reflect on your experience over the offseason and make any changes or upgrades as you see fit. then you can make more educated choices.
with that said, after cooking on WSM's for @ 5 years, if there was any budget for me for this wonderful hobby, i would invest in 2 humphries half pints for competing.
good luck out there.