I think there are several key advantages to the district model aside from having a higher shot at going to world champs:
Two competitions offers a chance to learn and improve.
As antman says, going to multiple competitions increases your chances of qualifying. But it’s also, I think, a key part of the engineering process. You come up with a design, you bring it to the “market”, and you see how it performs. You then have a chance to walk away, gather feedback, make changes, and try again. The lessons learned from the first go-around and the ability to come up with quick, low-budget fixes that you can apply between events, are really crucial. Plus, if you perform poorly or encounter problems, you can leave with a sense of “we’ll fix this and try again!” rather than “well, we failed and gave up”. These grow the team much more than “we won” or “we didn’t win”.
Teams that had the ability to register for multiple regionals as opposed to just one always had a leg up, both in terms of FRC chances but also in the learning total experience offered to their students. Districts brings this to everyone.
Making it to district championship is a success of its own.
As Michael Kaurich said, the feeling of accomplishment in advancing to the state/provincial championship is better than playing at a regional and simply not winning. “We made it to the state/provincial championship” is a success story on its own. It’s good for sponsors to hear and it motivates students. Our students were watching the standings eagerly and dreaming up ways both to improve ourselves in case we qualified (we just found out we did!), as well as how to improve the team processes next year so we have a higher chance of qualifying.
We’ve done two district events and are planning a third road trip for district championship. The students feel like we’ve achieved something tangible, which we have! It’s been a good year.