I've owned a few of each, and say that the twins are much more fun to ride around town... the extra torque makes stoplight-to-stoplight riding is better IMHO.
The 4's are more exotic (perhaps a bit huh?), less common and smoother, but I like twins.... the fours are boring around town, but less tiring on longer rides.
"punkrocks what it's all about" - J. Strummer
Originally Posted by Stagehand
your bike is suitably dirty. Well done.