The yamaha R1 (1000cc) is argueably the best liter class sports bike now.
The CBR 600RR is my personal favorite for 600 class bike.
The R1 does 0-100km/hr in 3.8 secs
While the CBR does it in 4.0
So if doing .2 of a sec slower than a 1000cc is imporant to you and you don’t mind sacrificing some of the extra agility that a 600 would provide then get the 1000cc by all means.
Of course the R1 has a much higher top end than the CBR…but I only know of one road in Taiwan where you could reach it on.