Compared to the Ice Fortress, the Glue Gunner is good on the aspect of directly slowing down bloons and getting the expensive corrosive path-1 upgrades or getting maximum glue power. The Ice Fortress, however, allows Ice Monkeys to freeze for longer (tier-2) and freeze all types (tier-3). Both Specialty Buildings are related to slowing to avoid overuse of combinations of Ice Monkeys and Glue Gunners. Despite this, a 2/2 Ice Monkey could still be used in conjunction with a 2+/2+ Glue Gunner and still make pretty good bloon stopping.