Binders are
not required for the FLL Challenge. Neither are posters (in Virginia-DC). Both can be a handy way to organize things, of course, and helping teams learn about good ways to organize and present information is a great way that coaches can help them to improve their skills. They are also great ways to record and remember what a team has done during the Into Orbit season.
You can see the rubrics that the judges will use at
http://www.firstlegoleague.org/sites/default/files/into-orbit/first-lego-league-rubrics.pdf. A Project presentation might address all 9 skill areas on the Project rubric. If a team has an engineering notebook, or has prepared a binder as part of developing their project, then it's certainly fine to bring it along. There might be information inside that the team would like to show to the judges, as part of their presentation or in answering a question.
For Robot Design, it is very hard for the judges to evaluate Programming Efficiency without seeing some of the team's programming. There have been previous discussions on this list about ways that teams can do that.
Whatever your team decides, don't expect the judges to spend a lot of time with team materials after the teams leaves the judging room. Teams are judged on what they present during the judging sessions, and there really isn't time during the day for the judges to pore over additional materials.
Those are my thoughts. I've done a lot of FLL judging, but I've never been a coach.
Steve