The article I read about the Benelli, was that the Honda motor wasn't under any patent/copyright....so benelli "shamefully" just "carbon copied" the honda motor, and added 2 cylinders. Granted, they changed the mounting of the alternator on the 750 version if memory serves correct. a Benelli 750 is a 500 with 2 extra cylinders, the 900 is a 550 with 2 extra cylinders.
Using modern technology, you could build more power with your four, but the sounds, look, etc. make the benelli a cool way to go. A straight six is just sexy as hell in a racer, huh?
That said, I'll just stay with the four.
~Joe