I recently had reason to list the different forms of shop heaters I've "experienced" over the years. I've worked in unheated, dirt-floored sheds that were little more than windbreaks. I've worked in shops heated with overhead, forced air LP heaters. I've worked with kerosene-fueled "blast" heaters, I've worked in shops heated by a wood stove, and I've worked in shops with furnaces fueled by with waste oil. I've worked under CoRayVac-type heaters hung from the ceiling, and I've worked over concrete floors laced with hot water heating tubes. Here are my conclusions:
Any heat is better than no heat. Kerosene heaters stink and tend to roast one side of you while the other side freezes, until the whole shop finally gets warm. LP heaters are nice, and you can't beat the toasty heat from a wood stove if the shop is well insulated. Waste oil furnaces are okay as long as the waste oil is kept clean and filtered---the actual heat is equal to a good LP furnace. I'm not a fan of the CoRayVac-style infrared heaters because I work on top of combines a lot, and they tend to overheat objects close to the ceilings. The absolute best form of heat--in my opinion---is in-floor hot water heat. Shops with floor heat are uniformly warm from floor to ceiling, wall to wall, and they warm up fast even after a big overhead door has been opened to move equipment in and out.
The downside of floor heat in a shop, especially after lunch, is that it's very easy to get drowsy, laying on that nice, warm floor when you're working under a piece of equipment. I guess that COULD be considered an advantage.
The bottom line when considering how to heat a shop is to be realistic about how much time you'll spend in shop during winter months. If there will be someone in there 4 to 6 hours a day, five days a week, then a premium heating system will be worth the cost. If you're a fair-weather mechanic, and can do all your necessary repairs and maintenance during summer or on warm winter days, then kerosene or LP heaters are cost efficient for the times you have to brave the cold. "Dream" shops are nice to fantasize about, but "real" shops are easier to pay for.