My team has shifted dramaticly over the pas three years. My first year, I didn't see the completed robot until our first competition. Last year, however, the robot was over 90% student built, but our robot struggled to move. Having seen both sides, I would say that either a 100% student run team or a 100% mentor run team can be very successful in achieve FIRST's goals. Students on a mentor run team get see exactly what it's like to be an engineer and can still get exited about it. Students on a student run team get more first hand experience on what its like to be an engineer(that is, if they have at least one mentor guiding but not at all building), although it's a little less accurate, and can also get excited. The purpose is to inspire. Whether the robot is student built or mentor built doesn't matter, as long as their still getting kids exited.
Long story short, it's not about who, it's about how.
That said, our team decided this year the "how" is easiest if both students and mentors work on the robot.
As for saftey glasses, their much more fun to wear if you custumize them.
