I'm 5' 10" 205, and I use the XL-XXL. Fits a little loose, but I'm usually wearing a few layers + I load it up with crap!
Watch out for sales, the line is changing...
The SE III switched to Treklite for 2012, but not in MO Bottomland, which is still primarily cotton, and prone to falling apart faster, and not holding a camo pattern as sharply.
I've had several SE III's fall apart with heavy use, no complaints, but the Trek-lite appears to be much more tear-resistant. Bought one in APG, and sold it, but the guy loves it!
I do wish it came in MO Bottomland Trek-Lite, that would be a hot seller, but MO said they had no plans in doing so. Maybe by 2013, they will change their mind.
mudhen