I think it really only depends on your budget and what you're willing to spend.
A 18" WSM will cost you $300.
A Brinkmann Gourmet Charcoal Smoker will cost you $80 (and you can find them for less).
For about $25, you can modify the Brinkmann and it will perform EXACTLY as the WSM.
So, it's $100 vs $300.
I'm not knocking the WSM at all, but even the VWB website suggests mods to it to better it's performance.
The ECB can be a fine weapon to BBQ with. Period. I've even done a side by side cook with mine and a WSM and they both performed IDENTICALLY.
Buy and cook with whichever you want. Good luck either way.
All I'm saying is that you can have 2 modified ECB's and STILL not spend as much as you would on 1 WSM. Fact.
Big JT's Smokin' BBQ Competition Team
"The path was worn and slippery. My foot slipped from underneath me, knocking the other out of the way, but I recovered and said to myself, 'It's a slip and not a fall.'"