The only way that stainless steel will pay for itself is if you fish in areas where you will be hitting submerged structure with the prop. Otherwise, the aluminum prop will serve you well.
Where I live in South Mississippi, we have to have stainless steel because we hit stumps and logs on practically every trip. I was reluctant to spend the excess cash on a stainless steel prop at first but after ruining two aluminum props, I could have purchased one stainless steel and never had to buy another. Lesson Learned