My favorite is the Russian plum magazines. They were made by both Izhmash and Tula, but you're only likely to find Izzy ones for reasonable prices. I can't really say why I like them more than the Bulgarian mags, it's purely subjective.
After that I'd definitely go with Bulgarian. Circle 10/21/25 magazines are all made to the same specification. Generally speaking, surplus Circle 10 magazines are only seen in black. Apparently there was a plum model as well, it's exceedingly rare. K-Var also has new production 10s in OD Green and their plum color (which is quite different from the surplus plum color). 21s are seen most commonly in black, but also in shades of dark red and dark brown. K-Var (Arsenal) also imports 45-round Code 10 magazines in black.
I've also used Bakelite magazines of East German origin and they work well. While they definitely look great, particularly on a rifle with wooden furniture, I'd go with Russian or Bulgarian polymer magazines first. The polymer magazines are more durable, but that isn't to say the Bakelite magazines are weak.
I don't have any experience with Russian Bakelite (at least not in 5.45) and I don't have any experience with Polish polymer magazines or the steel magazines that are available.
More information can be found here. It's not a completely exhaustive list of every 5.45x39.5mm AK magazine ever made, but it's a pretty through breakdown of any that you're likely to see in the United States.