[mseebach]

What is the difference between having people complete a project that's especially crafted to include "a nice number of data structures" that the candidate should be prepared to be grilled about -- and then just asking the question up front?

It seems to me that you'd at least have to forego most of the grilling bit - explaining why I made the design choice of using a list instead of a set (or the other way around), and what the tradeoffs and what-ifs are is just a roundabout way of asking "what is the difference between a set and list?" -- and if that's what you really want to know, skip the project and just ask that.