Move up a class and consider the ZX 9r, one of the most powerful engines even today. Kawasaki´s last longer than Honda´s and parts are less expensive. However the CBR 900 will beat the Kawa. So really if you want the best Honda is the best all around bike in both 600 and 900, but you can buy Kawa cheaper second hand!
If you can´t decide get both bikes and then you can make a scientific comparison yourself over some time ---- if you can afford it get CBR. Otherwise Kawa is also good --- the extra weight makes it more stable....and how fast can you go in the city anyway?