>>4614189People get 60mpg on a 250. Most I've had on my Sportster is 45mpg, I usually hang in the low 40mpgs where most bobbers/cruisers/cafe racers sit. Be careful of air cooled engines. Once the weather hits the 90s, you'll likely have to deal with overheating issues in traffic.
If you ever plan to ride 2-up. They 250 isn't really an option though. But that's where the 650 comes in.
This is all from the viewpoint of practicality. Where I'm at now, I wouldn't trade my Harley for anything. Sound/style/feel/comfort also play a role. If you check out a Harley dealership, they will likely have some nice used modified bikes for you to check out and sit on. Most dealerships (if not all) have buells and other sportbikes sitting in the back that you can look at, compare side to side, and sit on as well. You can read as much as you like about them on the computer, but the choice is made when your standing next to the bike with the engine running. I was completely set on that R6 until I stopped by the Harley dealership on the way home. He started her up for me and the sound sent chills down my spine, I totally forgot about the R6 after that.