The Fatboy has a very small CCW pouch, so small that I didn't feel I could get a positive draw on the gun at all. My G19 would fit, but it was tight and drawing the weapon was slllloooww. I'm sure with practice it wouldn't have been as much of an issue but it wasn't just the CCW pouch that was small. The whole bag is much smaller than in looks online.
I plan on using the bag when I go to the beach in a few weeks to hold my gun and other items therefore I want something bigger than the Fatboy. The name is deceiving, they should rename it the littleboy.
For my needs I just wanted something bigger. I like the fact that the Jumbo has the H20 holder and I think I will be able to fit a lot more gear in it. YMMV. Hope this helps.