The F4 tape bonds to itself when wrapped giving you a very nice and very thick insulator. It can be prohibitively thick. On things like 6v systems where lots of current is present, this stuff would help in preventing shorts on the larger wiring. Shrink tubing, although I use tons of it, is thin and works best in lower current applications. If you had a roll of F4 tape, you would use it. Sometimes the thickness would help act as a gasket for some custom app, another time you would just want to be sure you don't have sparks. If you don't have a roll, you wont.
I use safety wire in painting small parts. I can make custom hangers that aren't just shaped custom (like with a clothes hanger) but are designed to chain items together to stay in certain locked configurations so things don't flap around or wander when putting paint gun air to them. Once spun with safety wire pliers, you get a VERY strong system. I use 030 gauge the most but have used 040 for heavier items.
On my start cart which is basically a cart with a battery, gauges, gas tank, etc.. I used 3/8" heater hose (a 20 foot long piece of it) and ran all of my wires through it. Now if someone steps on it or something happens, the whole bundle is protected. They didn't even do that in the Air Force. When we wired whole airplanes, it was numbered, white wire with waxy twine to keep them together. (you have to be taught how to do this). Sometimes it was right out in the open so if someone was loading cargo and swung a crowbar or whatever, the wiring was toast. So, we wrapped F4 tape around the exposed areas as well as around every cannon plug to keep the wires tight. We didn't have zip ties in the day.
