If you have the ceiling height, (your 14' is enough), a tube heater, or in your case heaters, would be the way to go.
It will make it warm enough to work in there much faster, and save you a lot of money in the end.
A building that size, I would use two. That also allow you to heat the areas you are working in more.
I have worked in, and been involved in the building of many buildings like this. There is no comparison to the fast warm ups, and fuel cost savings.
If you use forced air, you commonly have to set the thermostat at, 68, or 72F, to be comfortable. A tube heater is radiant heat. Just like if it's a sunny winter day, you can feel warmth on your face from the sun, you will feel warm with radiant heat, well before the air gets warm. That allows you to set the thermostat lower. I usually like to work at about 64F.
The biggest difference, is when you have to open the doors to move stuff in, and out. Radiant heat is stored in the concrete, and the metal objects in the building, not the air. So, when you open the doors, the recovery is very fast. You are not waiting for the forced air heater to warm all the air in the building again.
Radiant heat is also much quieter, and easily made explosion proof, if you are painting, or have the potential of flammable vapors spilled in the building.
A radiant heater will warm what you are painting, even if you have ice cold air moving through there as you exhaust the paint fumes.
I would recommend forced air, if you have a small shop, with low ceilings, and don't need to open the doors a lot. You will still wait a lot longer for it to warm up though. The part of my shop I heat in the winter is, 30x30x9. It has a regular 80% forced air furnace hanging in the back corner. I also liked having the option to add air conditioning at some point.
