While you have read the plusses and minuses of both constructions, most folks buy on floor plan, cost and tow vehicle capacity. The outside wrapping is secondary.
Aluminum is older and evolved out of the old stick and tin construction. It is well established and lends itself to a range of price point constructions.
Fibreglass lends itself to the more sculpted designs currently in vogue, hence it is often considered more modern though it has been around quite a while. Fibreglass also offers a large flat surface for some rather detailed artwork.