can’t comment much on the too big CC’s based on the fact I went with 600cc sport and its not easy for a first bike for sure. I love mine and I’m committed to my parking lot practice as much as I am to getting out there and riding. I’m pretty sure riding a 250 would have been easier- but I’m stubborn as hell and I wasn’t going to buy a bike twice.
BUT if you don’t know how to drive a manual transmission in a car I totally suggest you learn that and then learning a bike won’t be a big deal cause you can focus on riding not the mechanics of shifting. (girl in my safety class didn’t know how to drive a manual or any of the side issues that present itself with one (i.e. starting on a hill etc etc) so she struggled a little bit more. But you can learn just out of the MSF what you need to get you through.