BR/Script (their PostScript emulation)
ethernet
duplex
And you will be fairly happy. If any of those are missing, you're buying an inferior line.
I currently have a Samsung laser toner (M2026W). I bought it because its farily compact and blends in to my little home office corner in the living room. The duplex machines tend to be a bit larger, a pitty.
Printing - when it works - is pretty good, just the WiFi is extremly unreliable and i end up having to re-configure the WiFi from scratch by connecting via USB and using some proprietary Samsung bloatware. Horrible.