Well, I can only speak with authority from my own experience, but I have heard a bit about depression era manufacture being smooth surfaced. My first inclination was that it was machined or sanded smooth after casting. I've also heard that a lot of folks from that time and more recently have taken to sanding and/or wirebrushing the surface of cast iron to remove the old seasoning and rust on "recovered" pieces, which would also lead me to believe many of the older pots would over the years have a smoother surface than the typical cast items from further back in time, or newer ones that haven't been neglected. Wear and tear would tend to smooth the surface of old pots and pans I would imagine.

Most of what I have is new. A few pieces are from depression era, and they are machined smooth on the inside. Some of the really old stuff I've seen is just as rough as the new stuff. The early american stuff I've seen (home cast, mostly spiders and such) are very rough, but well seasoned and quite functional.

In any case, I find the smooth surfaced stuff to be more difficult to season properly. I've never noticed any difference in how smoooth vs rough perform if both are well seasoned. Once the seasoning overcomes the rough surface, I reckon they are going to work about the same.

Steel griddles are smooth, as are my steel baking pans. I season them as well, and they work quite nicely. I suppose everything is relative. I reckon since most of my experience is with cast iron that has a rough finish prior to seasoning it, that is the stuff I am most familiar with, and I am more adept at making it work. Good cast iron, rough or smooth, is still a good thing.