The 650R is a chef’s knife. Sharp, powerful, and will cut you if you don’t respect it.
The ZX-6R is a surgeon’s scalpel. It is extremely sharp, does exactly what you tell it to, even if that is just an unintended movement, and will do very serious harm if you don’t know how to handle it right.
By comparison I’d call a 250R a nice camping sheath knife. It’ll do anything you ask of it, it still takes some respect and control, but it is weighted well enough to comfortably handle most anything with it without cutting you.
If you don’t work with knives on a regular basis, this comparison might be useless to you