Roof cap for exhaust fan

Have seen several options for roof caps to terminate a 3 or 4" bath exhaust fan duct through the roof.

L's and HD have Broan/Nutone steel cap w/epoxy finish. Have also seen aluminum and plastic version by Lambro (brand carried at L's, the roof caps are not stocked, but can be ordered).

Any thoughts/preferences on which material is best for installation and durability?

Thanks,

Joel

go metal

uv will break down plastic in 15 yrs