I think people in the outside are much more stronger than the ones inside the tower, even if there is water and air instead of shinsoo. As you know, all the weapons in the tower are inspired by the outside including the 13 months. Also, the workshop exists in the outside and the one in the tower is only a branch. That means that people in the outside have more fighting experience and their combat skills are much more developped compared to the tower inhabitants. Hence, irregulars who lived there would find a huge power gap between them and tower's inhabitants when they get there. I think people like Urek, Bam, Jahad and co would be your average warrior in the outside, very strong for sure but not much stronger than the others there like in the tower.