Generally, IG filters are sturdier, more realistically rated, and more functional than AG filters.

By the way, even with thermoplastic, you should be able to get a temporary patch that will leak a little, but allow you use the filter for awhile. Also, thermoplastic is not saying much: PVC and PE are both thermoplastics, but PVC can readily be patched with epoxy. When they told you it was thermoplastic, about all they were saying was, "It's not fiberglass".