Alupanel, Dibond, PolyMetal are all names for essentially the same thing, though each mfg is different and each has shorter/longer warranty. I think Dibond is longest and typically costs more than some of the "knockoffs". We got away from the Alumalite for the same reasons mentioned, but it is a lot stiffer than the Alupanel. So, for a sign that has to span between posts, Alumalite is superior in that regard, but the problem of denting is still present. In that case, MDO or PVC are probably better choices (though I know some don't like to use PVC for exterior apps).