Engineer ringing in for Team Lightning - 862.
I see good things in both sides of the equation. Those team with huge student design and build responsiblities will most likely get more hands on work, get a feeling of ownership in the robot, get to try things out and learn by trial and error which is better than being told what is right. ON the OTHER hand, those student's who get to watch good engineers work get to see how much hard work, hard thinking, detail work goes into something like a robot, and they get to learn good engineering practices (assuming the engineers take the time to explain stuff, which I assume most of these engineers do.) With that said...
Team 862 uses an engineer to machine alot of the metals because the machine shop has safety concerns. But he's not a professional so it looks like it's student machined.

But almost all of the robot is student designed, layed out, put together, tested, rebuild, tested, rebuilt, tested, and and the program and controls are 100% student done. Me and the other engineer spend most of the time making sure the students don't hurt themselves, buying pizza, and helping with "design issues".
I like both styles of robots, both are good. (Now my students are going to tell me I need to get an engineering team together next year so they can have a WINNING robot, instead of Ziff2.0) (JUST KIDDING GUYS!)