I use heat mats (i think its different to tape see pic below.) and I use heat cable.
The mats are expensive because as heat rises you need one for each tub and a thermostat for each level of rack to get the same temperatures from top to bottom.
My pros and cons:
Heat mats over tape. with a long strip temperatures rise the higher you go. So each level is a different temperature., but its cheaper.
Heat cable-
Pros: cheaper than mats or strips. It also gives a better heat gradient if put at the back wall and balanced right so the animal has more choice. for example, with a mat or strip, the first third is exactly the same temperature, no gradient. Jigging the amount of cable on different levels avoids hotter tubs the higher you go. Adding aluminum tape to it also even out the output. Probably my preference.