I have always run aluminum because:
1. I can buy 2 aluminum for the price of one Stainless, and that means I have a spare. A spare means I can always get home.
2. Aluminum props can be repaired, Stainless usually can not, unless you find a shop with expensive and specialized equipment (that means you'd pay more to fix a stainelss, than to buy a new aluminum.)
3. When your prop hits something, either what you hit, or the prop, or the shafts and gears in the lower unit have to give. I'd love it if what I hit gave up, but usually the rock or log wins that fight. The prop is far cheaper to fix than the lower unit, and aluminum gives way, and bends, well before a stainless would. So yep, you will damage an aluminum prop more often, but you will be protecting the expensive lower unit. My motor is a 1995 Merc, I ripped upabout 7 propos in the 11 years I've run it in the Ohio River, and spring at Cumberland twith the log jams afloat. The lower unit is still the original one, and still humming along.

4. And the last reason......people very seldom steal aluminum props off boats. But, you'd be surprised how may $300-400 stainless props got bye-bye. I have never seen a boat with a cheaper aluminum prop have a propeller shaft lock on it. I've seen many boats with stainless steel props, locked up for security. So you save money on the prop cost, and you save the cost of buying a propeller lock.

But then again, I run a pontoon, and speed is something I dream about.