A bar stool is typically tall enough that you need someplace to rest your feet. With that in mind, the 2 legs with the stretcher would go in front. I made a 3 legged Windsor type stool for my shop, like your first picture, to sit at when I can do something sitting down. Not quite as tall as a bar stool. It has a round seat. I find that sometimes I want to rest my feet on the rung, other times I put the "center" leg forward so I can have my feet on the floor and brace myself when working. The round seat also allows one to swivel around easily. You could make the legs, then try a shaped and round seat made of softwood on them and see which one works the best for you before making them out of hardwood. Maybe you will end up with several different seats! That would be a conversation starter.