Thanks to everyone who took the time to comment here and elsewhere.

This wasn't exactly a scientific study but the results were very interesting. Everyone agreed the VHS source was both the worst looking and easiest to identify. However it seems the differences in quality between the final two caps were too slight for most, yet the majority of guesses were shockingly accurate. But which screen caps came from what video source? --

Screen Cap #1: DVDr by way of DirecTV broadcast recorded, in SP mode, onto the internal HDD of a Panasonic DVD recorder, prepped, then burned to disc.

Screen Cap #2: DVDr by way of an SP mode VHS prerecord, label: Vestron Video, played on a Phillips S-VHS player hooked up via S-Video cable to the same DVD recorder mentioned above. Recorded and burned in SP mode.

Screen Cap #3: The commercial DVD.