I had a 2010 Fatbob that I bagged out and was working on blacking out when I wrecked it. I now have a 2012 Fatboy Lo. I like the lo a lot better. Its got floorboards which makes it a lot more comfortable, it doesn't ride quite as smooth with the lowered suspension and has less ground clearance but I don't really ride fast through twisties anyways. The Lo is bigger and will accommodate bigger bags which I really like. The Lo is also a lot better looking bike also and I think easier to work on with the softail layout.
Other than dragging the floorboards a bit, (its not a sportbike so i dont care) the Lo is the way to Go. The cool factor is great and it rides great as far as im concerned. Great bike.
I was in your position a while ago. My perfect bike is somewhere in between a fat bob and a fatboy lo. It'd be too expensive to buy a bike and chop and change it, so I recommend the fatboy
Rode a Lo from San Diego to Vegas and back...nice ride, but if you are a bigger guy (6' or over), you may need to change the seat/handlebar setup. Nice looking motorcycle though.