A pole barn is going to look like however you finish it.
I've seen lots of them with no walls used just for storing hay.
Or you can completely finish off the outside with either metal or wood. How it is held up on the inside makes little difference to the outside finish.
I once worked on a huge steel framed building, where we built a bunch of 2x4 walls to fit in between the steel pillars, anchored them with a .22 nail gun, and then sided the outside with board and batt. I had people tell me later that it was a completely wood framed building
I don't think pole frame construction is very efficient
when you are going to finish the building inside and out, because you end up framing the structure twice: first with the posts in ground and then with all the 2x4s to hold the siding, sheet rock, etc. Would be faster and cheaper to just frame it with studs to begin with.
The advantage of pole barns is no foundation. If you're going to put in a slab later then you might as well do it up front and make it easier to build.
We're wanting to build a mostly enclosed hay barn, and will probably go with pole barn construction because it will just be dirt floor. We'll put pallets in to set the hay on, and one end will be open for the horses to run in for shelter and to be fed, with some steel panels for separation.