There are a few reasons I have decided to stay with the aluminum siding, even though I once swore I would never own a camper that looked like it had house siding on it.
Looks: I like the way the glass (Filon) looks when new, but there is a (small) part of me that likes the old school look of the aluminum. My girl pointed out that the smooth sides look cheap, and I can see where she is coming from, especially with plain white glass. If you color matched the camper to the truck then it is a no brainer. But I also think in the long term the aluminum will stay looking nicer, as painted glass scratches easily.
Longevity: I am sure FWC has done it's homework, but I have become skeptical about how long the glass will look good, and looks are the only reason to go with glass. Spider web cracks from flexing. Scratches from tree branches. Minor dings and damage. These things will be very obvious on the glass, but not a problem with aluminum. The aluminum siding can have sections easily replaced, but as best I can tell the glass is a one piece shell, so fixing major damage would be a problem. In the end I know that a ten to twenty year old camper with aluminum siding still looks nice, and I am not convinced that the glass will stay looking as good as it does when new. (Stan please chime in if you have any thoughts on this.)
Cost: (Edit: now listed as a $650 option.)
$400 is not a huge amount, but it is over 5% the cost of a shell and I am pinching every pinney to afford this camper. (Not sure how much having a shop color match would be, but I would guess an extra $500+.) So for myself spending the extra grand just for looks is a big consideration, a thousand dollars buys a lot of gas.
Weight: (Edit: Added weight is 37 pounds on a Hawk.)
Just as with cost, I am watching every pound on this project. Stan says there is not much of a weight difference, but on a Tacoma every extra pound makes a difference. So I would go with the aluminum solely based on a small weight savings.
So those are my thoughts. I reserve the right to change my mind at any point.