600's are for girls and Busa's and ZX 14's are for the dragstrip and stretched swingarms so I bought a litre bike.
Ok how about...I'm not so great in the twisties so I wanted some power to catch up in the straights but still didn't want anything as heavy as a Busa or ZX 14 ?

I didn't really want a Buell although I do think they are cool and also didn't want to pony up the $$ for a Duc although I do like them alot.
Ok on a more serious note even though my 2nd paragraph above is closer to the truth than my totally joking BS first paragraph...I just really like the R1.
I owned a 2000 R1 several years ago and just like it better overall than the other 3 Japanese litre bikes. I think the R1 looks better than the other 3 and at my level of riding ability they are all close enough in performance that it didn't really matter which one I chose.
I would have been fine with a 750 and probably any of the 600's too since they are so vastly improved over the 600's I owned in the early to mid 90's.
I bought an R1 and R6 thinking the R6 may be mainly for the track but the wife has taken to riding like a duck to water and she laid claim to the R6 and even put some pink flames on the windscreen and a "Girl Power" sticker to mark her territory and to keep me off of it.