Franchise model has more stability, for owners and fans.

The drawback, depending on your point of view, is that it's locked down. No one can force their way into American football, without permission.

In European football, you or I could conceivably start a team tomorrow, and we could hypothetically be in the premier league in a few years.

The downside, major cities could be without a competitive team, the team you've always rooted for could fall apart.

Franchises can be anticompetitive, which is why they do things like drafts and salary caps to help maintain equilibrium since there are no external forces to balance it.