RE: 21x14 or 20x13???
I've got pretty much all the different diameter and pitch props, and I prefer the higher kv motors with the larger diameter and less pitch. Actually the one I always end up going back to is the 22x12 on 220kv. In all but the heaviest winds I prefer this prop. Gets more of a constant speed, at the end of the sequence has enough thrust to pull through the radius on top, downlines I don't use any breaking. Real heavy wind I'll use the 21x13.5. I just don't like the high pitch props. The axi at 235kv I used 22x11. 20" props I don't like at all.