That's wrong, the 750 was always faster and torqueier in a straight line but always heavy and subpar in the bends throughout its model history. And making it a better handling bike required a lot of money.
The Reason a bike would be Subpar in a bend is, Suspension not set correctly!
750 setup correctly will eat a 600/650 on the straight and easily stay a head in the bends
Getting your suspension to be correct for you is a case of getting the correct springs and oil weight.
Do this and a bikes handling can be transformed, inspire confidence and for road and track day use more than adequate.
If you want to go and blow Thousands on suspension go ahead but most sports bikes from late 90's till 2008 had suspension that had compression, rebound and preload settings which is highly tunable.
Unless you are riding at competition level this is more than enough.
If you only have standard hydraulic suspension with no adjustment again the right springs,a set of emulators and the correct oil and suspension is night and day better for two to three hundred pounds.
The options are out there and not for mega bucks
If your suspension hasn't been serviced then this will also cause your bike to ride an old donkey 10,000km 6000miles service limit for forks and shock.
If it not been setup for you it will ride like an old donkey.
if you've never had this done, how would you know the difference.