I have had both aluminum and fiberglass. I prefer fiberglass.
Fiberglass is heavy but looks better, it can delaminate, aluminum can dent. I find glass easier to maintain, other prefer aluminum.
I don't think you can go wrong either way. If I had to guess I'm going to say the number one priority for aluminum is weight savings and cost.
2009 F350 CC LB 4WD
2017 Jayco 355MBQS