Main thing to remember is the ZZR is a sports/tourer whilst the GSXR is a sports bike. The riding position is more extreme on the Gixxer, especially if you have a long inside leg. Although former GP rider Kevin Schwantz has a 34" inside leg and he did "reasonably" well (lol !!).
You may find it a bit cramped compared to the Kwacker.
It depends what you use the bike for..and how often you need more than 150mph
I've had a reasonable cross section over the years. CB200,CB400,DT250MX,CX500B,CBR600,VFR750FL,GSXR750,GS850G,GS1000, CBR1000,GSXR1100M, CB1100 X-11, and after years of ridiculing "tractors", I now have a "Hardly Movinson" 1200 Sportster...and I luvs it !!
Ok, it ain't a standard motor..and it handles and stops like a pig on a pogo stick, but there's just something about it.
I think it's the fact that I just can't ride "head down, @rse up" bikes sensibly. where as the H-D still has plenty of stomp, a certain BMW M3 driver learnt that. (mind you, that surprised me too !) but also there's "that sound".
What ever you go for...if it makes ya grin, tha's made the right choice !!