Hello Michael,

and welcome to the TFG-discussion board.
What is the intended use of the barn? My personal preference for the barn floor would be concrete as it is durable and will not rot. Also you do not have to worry about driving a vehicle into the barn and wether the floor is strong enough and so on. Especially since, like you had mentioned, you will not be able to see the fancy (or not?) floor joist joinery.
I can see a lot of folks jumping out of their seat right now and wanting to argue that this is not traditional. But I think it just has to work and last. I always like the look of a concrete slab with a 24" stone wall and the frame on top of that.

Here is a question for you: What, if you do decide to go with a wood floor system, will it be resting on? Stone? Piers?