If price doesn´t matter I would chose the CBR954. For overall riding you won´t have to wring it out and put up with high frequency vibrations like you would on a 600. This is not a critisizm of the Yamaha, it is just the difference between a big bore bike and a small bore bike. If weight is a factor then the 600 is your bike of choice, although I seem to recall that the 954 was one of the first "big" bikes to achieve weight and size similar to a 600.