I only took a ride up and down the street on the kawasaki 650R
it felt like a good bigginer bike.
I have a little over 3,000 miles on a 600 ninja, ( ZZR600)
The differences are many,
Do you want a bike good to go to work. ride slower, and is more simple to work on ?
Then the 650R would be good , along with insurance rates.
Do you want a bike for the Canyons ? a bike that handles better ?
Then the 600 or 636 is better , although you will pay a little more for a tune up's , and insurance.
See if you can ride both. What are you riding now ?