I would only use substrate cables if I couldn't grow anything without them. The frustration incurred the first time I transplanted anything with a root ball would be the end of the cables for me. I won't go into problems they create in warm weather.
I have a 10 gallon on an iron stand under another aquarium. It's about 2 inches above the floor in a house with the thermostat set at 65 in upstate NY and this has been the most brutal January I have seen since being here. The air stratifies somewhat, the floor is not up to 65 by a stretch. The plants for sure have cold feet, but this tank will grow anything I put in it quite well. It is about 2" of quartz gravel with 10% Flourite mixed in over about 2" of Profile, amended only by mulm produced in the aquarium. This is by no means a scientific experiment, but it's more than enough to keep me from ever giving substrate cables a second thought.