GSXR1000 K5 and K6..... why is it held in high regard?

[BuzzBravado]

I keep getting drawn to the Limited Edition ZK4 in black with gold wheels as my next low cost care-free bike. But one thing in the back of my mind is that the K4 seems to take a back seat in favour of the K5 once the internet gives its advice.

Looking at wikipedia there isn't much in it apart from the K5 being shorter and prone to cracking frames.

https://en.wikipedia.org/wiki/Suzuki_GSX-R1000

So if i went for a K4 simply because i prefer its appearance am i going to be missing out on much? What is so special about the K5 and K6?

[BuzzBravado]

I see the engine in the K4 comes from the K1 unchanged over the years so i can believe the K5 engine has been updated a lot. On paper the figures look very similar though.