1. Depends on what you plan to tow it with. I would rather have a lighter trailer in order to not max out a TV (tow veh.) Alum is lighter than Filon and glue.
2. They both will age over time and decals are decals, they fade and peel and crack.
Keep both washed and well waxed and remove oxidation and they both look like new. It takes a little more elbow grease to keep the alum. waxed.
3. Alum is easier and less expensive to repair and can be repaired by anyone with basic skills . It can also be repaired in sections opposed to an entire side.
4. Its a little bit more difficult to maintain caulking around the corrugated aluminum but its not difficult, just takes a little more time .
5. Aluminum will not delaminate because its not glued to the trailer as Filon (seamless thin fiberglass type sheets) is. When water intrudes the Filon, the glue becomes saturated causing soft spots and delamination. This is very time consuming as well as expensive to repair. Repairs are made by pinch rolling the Filon because most people and RV repair facilities do not have the means (expensive eq. ) to vacuum bond it back to original condition.
6. Some prefer Filon because they like the smooth look and find it easier to clean.
I have owned a few of both and prefer aluminum due to the weight. The extra time cleaning it doesn't bother me. I'm fortunate to have my health to do it and that's what matters. All else is just personal choice.