Bootcamp was the most representative of the actual DAT in terms of timing, test format, question style, etc. Destroyer isn't a resource that's designed like a practice test - it's a series of questions used to build up your base of knowledge that's still extremely helpful. Qvault has practice test format but a lot of its questions were off the mark in terms of difficulty (usually too easy or randomly specific) and very repetitive in some subjects like general chemistry.