I’d go fiberglass if Trident (or some other mfg) made one small enough to fit in my propane locker. To my knowledge, none do.
My propane bottles have begun to show signs of rust, so I pulled them out this summer and coated one with spray-on Flex Seal. An experiment to possibly keep the rust at bay for awhile. The other remains at home (hooked up to an Ooni pizza oven — it’s handy for that!)
We don’t use our propane stove/oven heavily. For now, one tank is plenty. Plus we have an adapter that permits us to shift over to a small disposable propane bottle, the same kind that we use for our BBQ. We seem to be able to go a long time on just one of those bottles. If my propane tank rusts out too quickly, I may shift over to those entirely. That is, unless a fiberglass tank becomes an option — if that happens, I will upgrade to one of those.
Gini