Read the article on “Why 600cc is too much”
A Banshee is a 4 wheeler not a motorcycle so there are huge differences to adjust to. It will help in your clutch, shifting and throttle control but handling and braking are much different.
A Ninja 250r is a great starter bike but if you feel you have to have more consider bikes like the Ninja 650r, FZ6R, GSX650F, EN6r, SV650 etc. These bikes have lots of power but not quite the race tuning of the supersports. Probably more importantly the handling a sitting position is more upright and relaxed making for an easier learning curve on handling.