I have both an Arsenal and Krebs Kalashnikov, I'd say that the Arsenal's action is a little bit more refined and the finish is just as good if it's an American Arsenal produced gun, powder coated, not one with the military finish that's just baked on. Attention to details is about the same, maybe Krebs smoothes out the sharp edges a bit more in some places.
Here's my Arsenal SA M-7 Carbine, same livery as the Iraqi National Guard Kalashnikovs.
But pretty much any custom builder like Krebs, AK-USA, ARS, AZEX, Inrange, IGF, Firing Line, etc is going probably equal an American Arsenal in quality. And you can’t get customization through Arsenal. But if you want a stock milled AK in any color you want as long as it’s black or blonde, Arsenal is the way to go.
VEPRs are third down on my list of refined Kalashnikovs. The actions aren't as smooth as an Arsenal or Custom build. But they are very accurate and robust and a very, very good value for your dollar... if you can get one in a rare moment when Robinson and Molot aren't in a hissy fit with one another and don't mind a little extra weight. I'd personally get the 20'' Vepr II 7.62x39, put a bipod on it and you've pretty much got the best dollar for dollar RPK type gun on the market. The Vepr K 7.62x39 is the other one I'd recommend.
Vectors feel about as rough/smooth as the VEPR action, a good option if you want a decent Kalashnikov that isn't put together by monkeys. I suppose they'd have about as good of accuracy as a standard satellite state military Kalashnikov. Though I hear Century Yugos aren't too bad, hopefully I'll be able to inspect one in a little bit when J&G Sales gets them in.
Or if you're a manly man, you could always WECSOG one together, practice like hell with it and make all of us high dollar Kalashnikov stock-pilers weep like little girly men on the range