…in the McLuhan sense.
“Hot media are high definition (“well filled with data”) and demand a relatively passive audience; cool media are low definition and require intensive audience participation to fill in the blanks. Hot media intensely engage a single sense; cool media loosely engage multiple senses. According to McLuhan, movies and radio are hot media while television and conversation (on the phone or in person) are cool ones. Print is generally a hot medium (the eye must closely follow a linear arrangement of symbols) but can be cooler depending on context.” – Cecil Adams
From this (I don’t have McLuhan’s Hot & Cool within reach) I say cool – require intense audience participation and are low definition.
For reference, television and phone conversations are ‘cool’ – while movies and radio are ‘hot’.