My garage is set for heat, but I have yet to install the furnace out there. When the house was built, I ran the gas line from the basement to the garage. I don’t see a point in installing a heater until I finish insulating the walls and putting up drywall. The flip side to that is it will be heated with the propane that I use to heat the house, so the tank may need to be filled more over the winter depending on the use. Being the garage, I would only use the heat when working out there, and set the temp around 40 degrees, just enough to melt the slush off the truck overnight.
I have also researched the infrared electric heaters. They are supposed to be quite efficient but I don’t know anyone that uses one. The cost for one of these units is about the same as the heater my garage was originally designed for, and they cover up to 1000 square feet (my garage is 1100).