Stick size matters not when talking about ability.... it matters when you consider what style of music you are playing with your sticks. 5a, and 5b are perfectly suited for learning technique and rudiments.
I use 2b when the volume and style calls for it. If i try to play with 5b's with my main project (heavy groove metal) I'll go through them like a buzzsaw. With my two cover bands I use 5b's always, because of the decreased volume, and increased chops needed.
Use what you have, and when you're ready you can let your musical aspirations decide which equipment will be best.