The aluminum wrench is for wrenching, and the cast iron wrench is for beating. There isn’t a difference in durability in the aluminum or iron pipe wrenches. I find it doesn’t make a difference to me. Unless you’re using them all-day.
Aluminum wrenches are ideal for jobs in tight spaces and overhead applications. Designed for easy access in close parallel lines. forty percent lighter than heavy-duty wrenches.
Some prefer lightweight aluminum, but cast iron is fine and usually cheaper. Go with a good brand like Ridgid. The reason for Ridgid is they are well made and replacement jaws are readily available. For household use replacing jaws will probably never come up. It takes a lot of use on steel to really wear them.
Aluminum is just lighter. If you have to carry wrenches all over the place and spin them all day it makes a difference. If you use one every couple of months it’s not worth paying double the price.
The aluminum is just a luxury for those who use them constantly. The only reason I would consider it is the fact that it won’t rust in our super humid environment.