My Party had black doors, nothing wrong with them. Just keep a wet towel around your smoker and clean off the doors and handle after opening. Stainless is purely cosmetic and a little less to maintain, it looks nice and is a little easier to clean.
Just keep the black doors, sides, top, etc painted so it doesn't get surface rust anywhere. Most all of us get scratches on our smokers from time to time (especially those who cater or compete). I keep a bottle of auto touch up paint in my temp kit (small tool box with thermopen, taylor, pyrex, batteries, etc) so I can cover stratches as they happen.
Rust is the enemy. Prevent rust and your BWS stay beautiful.
And to help prevent rust on the inside, season that bad boy at least once a year with a good coat of cooking oil or lard. I was advised to use peanut oil. I do it once in the spring and once in the fall.
To season, get it nice and hot - over 350* for an hour or so. That will help the pours in the metal expand. Then while it's still hot, coat on the oil with a clean rag. Pam the corners so you get them good too. Then close it up and keep it up over 350 until the black smoke coming out during this process turns clear. Then close it up so fire will burn out. The oils will kind of bake in/on the metal to protect it - for lack of a better way to describe.
Backwoods Gator (former smoker)
Backwoods Party (former smoker)