Some important points to remember:
Low suspension 850 has a crap rear shock - I had one and hated it. It also cannot be specíed with ESA or a centre stand and there is no aftermarket alternative. Fine if you have paddock stands or an Abba stand but parking on rough ground or patching a rear puncture is so much easier with a centre stand. I wouldnít have a chain drive bike without one.
The 750 has less suspension travel but is still pretty soft so I doubt itíll bounce around less on hard braking. You get used it fork dive over time and work around it.
The 850 has longer travel suspension, upside down front forks, spoked skinnier wheels, braided steel front brake lines and a small amount of power that mostly manifests itself above 6K revs. If you want a road bike that can do a bit of light off reading with a lower seat height and centre of gravity, that is also > £1K cheaper, pick the 750. If you want more aggressive off-road, must have that extra top end power or prefer the looks, or think the very marginal increase in braking power is worth it, get the 850.