43 would be faster than a 44, and 44 would be faster than a 45 etc. Bigger pinion and smaller spur would create more speed, but WATCH YOUR TEMPS! 15/45 and 14/43 are very close to the same ratio, and that's what most guys around here run. Nobody I know runs a 44.

Remember, the fewer teeth a spur has, the faster it will rotate as there is less travel per revolution. And the more teeth a pinon has, the faster it will rotate the spur as each revolution of the pinion will create more travel and move the spur farther, thus faster.