If this is your first bike, and if you plan on doing much of the work yourself, go with the twin. This, coming from the owner of a CB500 and a CB550.
Half the carbs to fiddle with, half the valves to adjust, etc. Plus, they're a marginally smaller bike, thus, easier to handle for a new rider. Oh, and whatever you get, get it running and fine tuned and learn to ride it before you start cafe'ing it out.
My two cents....