I like concrete and you will use concrete in the construction regardless. Consider pouring thick footings, if you need frost protection, measure from the bottom of the footing for this depth requirement in your area so you can maximize the height that you can get an 8 foot (7'-10') poured wall. Note that you will bring in processed gravel for the base so use this gravel as a ramp to pour (for height) to save about $750 for a pump truck. Use 2 course 1/2" rebar in the footing and 2 near the top. Now you have half of your building complete instead of just the base to start your steel from. This will also give you a straight wall to work off of.
