I've ridden a spark, the owner told me this is the prop he used. Very punchy in the low-end and midrange. Would recommend based on riding. MPH was the same though.
There is a difference with this vs stock, and from what I could tell the stock motor was able to push it.
Wear ring is what is supposed to wear first, getting stainless steel makes it so that when you suck something up your nice prop is going to get destroyed.