So, I measured my inseam and it's 35" which "means" that I should be on a 21" bike. I guess those two inches make a pretty big difference. My brothers bike is 19" and it feels really good to me.
I think I'd rather have the MB over the XO since I will be using this off road use, and also for light commuting and around town. I really dig this bike! I might be impatient but I rarely come across bikes like this in Nashville. Although, I've been finding some sweet stuff here lately. I asked if he could come off the price a bit. We'll see what happens.
Again, thanks everyone for the help.