Spray foam costs more up front than fiberglass batts, but it seals air leaks, fills irregular spaces completely, and in its closed-cell form resists moisture, which fiberglass can't do. Fiberglass is inexpensive, easy to find, and works fine in the right places if it's installed carefully. The better choice depends on the part of the building, your moisture risks, your budget, and how long you plan to own the place. We install spray foam, so we have a bias. That's exactly why