Yeah, as my friend TreeBarber says, aluminum is just fine, though steel will wear better. If you're working in dirty circumstances, it can make a difference. You'll see aluminum wear if you're passing a dirty rope. Rock climbers that use 8's use aluminum because of their weight. They're plenty, plenty strong. Steel is used in rescue instances because of it's extreme strength and resistance to wear.
There's no problem trusting aluminum. If it wears, get a new one.
Jeff