Leather on top of velcro is 3 layers of softish & compressible backing, versus only one layer if leather is used alone on the wood. Personally, I'd avoid going in the velcro direction, as it makes edge-rounding more likely as the softish substrate becomes thicker. As mentioned, the wood is cheap or sometimes even free; I'd just make a separate strop for each compound used, and keep the leather as thin and/or hard as possible. Finished results will be better for it.
David