In the shop I ordered from they suggested to go with 20", in another shop I've been to, I was advised to go with 19". That's partly why I am scared away from 20"+ unless I have a chance to try it. In any case, those several inches don't make a critical difference?

Also, I am not sure, may be I am converting it wrong. I know that my height is 191cm and the inches thing comes from me converting it to that system, so may be I did something wrong.