Well I am going to speak from experience here. My first bike was a F4i 600. The damn thing was a rocket and it scared me. It would wheelie up easy with too much gas. I finally felt comfortable on it after a few months and learned how much gas to give it, how to corner nicely and I would even speed a little.

The one time I went down was my own fault. I left riding with the guys and canceled my gym plans. Well I had forgotten I had taken some Xenadrine RFA-1 and I couldn't concentrate. I ended up dropping the bike in a parking lot. Not much damage but it was enough to spook me.

I sold that bike and purchased a Hayabusa 1300R. I got it for the look and for bragging rights. The bike was a beast but I got it due to the fact it's not going to wheelie on you unless you give it an ungodly amount of gas. The fact it's heavy was great. I left it stock except for a Yoshi exhaust. They drive and corner like a Cadillac though.

I sold that and now I ride a Honda CBR 1000RR. Everyone learns at different paces and everyone will voice their opinion on what you need to buy. My advice to you is to buy what you're comfortable with. You said you're already recovering from a spinal injury so you're already going to be weiry and nervous on the bike any way. That's good. The bikes these guys posted are all quick and great bikes but they all have one thing in common, they will all kill you. No matter what you buy to learn on, remember that it will kill you when you lose respect for it. Not just hurt you or scare you but kill you.

I wish you luck bud.