This is the kind of gaffer tape I have always used in the theatre - it is a bit cloth-like and tears easily - good for holding coils of LX stuff, comes off easily when you need to uncoil them. I've not heard of duct tape - is it the same stuff that I would call insulation tape? - usually in thin rolls, you can use it when joining wires together, presumably because it has good insulating properties.

Funny for a nation which is so sure about "goat cheese" to use "gaffer's tape" when we say "gaffer tape" - there just ain't no logic with some folks!