All this angry back and forth about who is profficient and to upgrade or not to upgrade. In my personal opinion, you can't be safe on a bike that you don't FEEL safe on. If you are more comfortable on a larger bike, go for it. At least you were sensible and learned on a small bike and didn't immediately buy an 1800cc monster without ever putting butt to saddle(like my dad). Personally, I don't think that getting a bigger bike for myself would be an "upgrade" since I've met hobbits taller than I am and I like being able to put both feet down
Ride safe!