Neither one affects the performance of the stove however legs or skids determine how the stove can be moved and set into place. When it comes to installing, leg models save on money and time since you can see the piping coming up from the ground when placing the furnace in position, and you do not require a full concrete base, only four sidewalk blocks. The skirting and frames on all furnaces, including stainless models, are made from mild steel and are subject to corrosion when sitting directly on the ground. On leg models you will be required to build a simple foam box around the pipes above ground level. Check to see that the sheeting underneath is a solid sheet and does not have large openings for critters to enter.