I had a mid 2000's Ninja 500 at the same time as my wife had a comparable Ninja 250.
I can't understand why so many people recommend the 250 as a great beginner bike. I found the lack of torque made it harder to ride in the city than the 500. By far less forgiving. The Ninja 500 is a much better beginner bike.
I loved the 250 on curvy country roads, with no stop lights. A hoot to rev to the moon.
I bet the 300 will be the best of both, with modern looks, and ABS. I'd love to ride one!