I have been using FUH54 model by Fahrenheat for a long period of time. I have a medium size garage and it has been heating very well. As far as your question is concerned which one would be best and cost effective, I would say should buy an electric plug heater as it is not just cost effective but is also very safe according to my experience. There are also some other great options available for electric fan heater. I would recommend you to read the best electric garage heaters guide by [https://garageaxs.com/best-garage-heater/|'''Garageaxs''']