I've owned steel and Brass national tricones. The best way I can describe it is steel is Fender, and Brass is Gibson. German Silver is Gibson through the most harmonically complex clean amp you've ever played
I did sell my steel Polychrome tricone when I got my German Silver, a modern one bought used. But not because the steel sounded bad. I just couldn't justify keeping both, and the German Silver sounds amazing, and "classic", but also was my bucket-list guitar. When I started playing guitar as a child I took one lesson from the old guy across the street. He was a musician from back in the day who played with Turk Murphy's band, and he had a "real" Tricone on the wall. It made an impression I never recovered from! I never dreamed I could own one, let alone a modern one with the "right" material.
Buy used for three reasons:
1. There's a significant depreciation when you drive it off the lot.
2. Most people buy these and never play them. They are "harder to play" than a flat-top for many reasons. There's a learning curve, but it's worth it!
3. The finish is probably already compromised under the forearm, where the neck meets the body, and on the strap. So no worries!
I bought a 2001 Style N for $850. Is the finish mint? No. Does it look like Nickel National that was bought in 1931 and played actively until 1951? YES! No idea how that could ever be considered a bad thing!
Now if you find a used nickel one that looks mint, just give it a good clean and polish when you get it, and give it a good going over with pure Carnauba wax (like for a car). That will last you for months, and all you'll have to do is wipe it down after playing. The first time it isn't enough. Schedule in a cleaning and waxing. Easy peasy!