I have a pre-ban MAK-90 (Chinese) with an AK-74 type muzzle brake and a post-ban WUM-1 (Romanian in 7.62x39) with a "Made by me" muzzle brake, so I'll compare the two.
The MAK's trigger group is designed specifically as a semi auto. It has two hooks on the trigger vs the WUM's one. The WUM's trigger group looked like it was adapted directly from the military rifles and simply omitted any auto components in favor of spacer discs to take up slack.
The MAK's mag release is a little longer and wider than the WUM, so it's easier to manipulate.
The MAK's finish is simply thin blued steel vs the WUM's thick black (phosphate or parkerize?) finish.
Accuracy on the MAK is pretty impressive in my opinion. I've made some pretty good snap shots with it on rabbits (yes, rabbits with an AK). I was able to double tap a rabbit, offhand, from 100yds when the thing made the mistake of stopping to take a look at me. At one range, we were shooting at a plastic pole, about 2 inches in diameter, from 175-200yds and were able to hit it every time.
About the only gripes with the MAK is that the gas tube rattles like crazy on mine and the finish is a bit cheap. Other than that, no problems, no jams, no nothing! It's an AK!
Unless you don't have a choice, avoid the new AK's with the single column magazines.
[This message has been edited by Destructo6 (edited May 25, 1999).]