Infinite fortressses have no shields. High-rank Titan barriers are definitely better than an infinite fortress when you give the Titan barriers shields. A basic aegis barrier at rank 1 with the shield on is better than a rank 1 infinite fortress with no upgrades in my opinion.
Inf. Fortresses have status resistance and can decently tank shots that are laser reflected. It also has an upgrade that adds hp more that you could actually get 1k hp on a unit with a good setup. I feel that it cost less than aegis since you dont have to buy for its upgrades individually and in tech center.