The Spanish missionaries were as zealous as anyone can get and yet none of the native societies became particularly fanatical converts nor did they even convert completely really. I see no reason the Muslims would be much more successful in getting everyone to become Muslim fanatics when burning "heretics" alive in droves wasn't enough to create a society of crusaders.
Well, it's less about the Muslims being more capable and more thinking of how those who adopted Islam voluntarily often were fanatics early on.
But yeah, in terms of spreading the word in the first place, I'm not sure how Islam has an edge here. Besides possibly a more attractive message - and that's more how it's presented than Islam Is Better.