IMO, the following are what I see as pro's and con's of some of the more common final AK finish methods:
Blued pro's.....
*Apearance, apearance, apearance
hat*Because it does not hide blemishes, it also allows you to see any early on minor corrosion problems that some other finishes may hide until the problems become somewhat major.
*A finish that was an early on common way of finishing Com Bloc AK's.
Blued con's.....
*Does nothing to cover machining marks or blemishes.
*Offers least amount of corrosion protection when compared to the other common finishes.
*Requires a more concentrated metal polishing effort prior to bluing (a smoother final polishing of the metal will only enhance the final blued finish look).
*Scratches seem to stick out like sore thumbs.
Gray to Black Phosphate only finish (what many consider as Parkerized) pro's.....
*Because it usually is done over a bead or light sand blasted finish, fine metal blemishes are better covered up.
*Phosphate leaving a matte finish helps to further cover up fine metal blemishes.
*The combined bead blast/sand blast finish, coupled with the matte phosphate, leaves a porous texture that helps retain your oil protectents. Seems a bit tougher overall than a blued finish.
*The matte phosphate finish makes it easy for one to later use it as a base for a surface finish (like paint), if that is something that one chooses to do later.
*The appearance is pleasing to most. The reason for this can probably be traced to the fact that us Americans are very used to seeing U.S. military weapons having phoshate finishes, and it has grown on many of us.
Phosphate con's.....
*It can be pretty difficult to touch up scratches.
*It is only a little better than bluing in resisting corrosion.
*For many purists, it is simply not a common or appropriate finish that was used by former Com Bloc AK builders.
Paint (or the like) over phoshate pro's.....
*Of the three methods covered here, this one has the most corrosion resistance.
*Commonly used method on modern AK's.
*Somewhat easy touchup on scratches and such.
*Can be coated with extremely tough scratch and wear resistant finish.
*If the top coat is compromised, the base phoshate finish will still offer "some" protection.
Paint (or the like) over phosphate con's.....
*While the final surface finish "can be" applied very nicely, a surface finish (such as paint), may look to many as the least sophisticated of the three methods mentioned. Painted finishes are usually not considered to have the rugged military look of a phosphate only finish, or the beauty of a blued finish.
*Surface finish can hide rust, sometimes not letting you know there is a problem developing.
*Surface finishes can sometimes peel or chip, which is unsightly and very difficult to cover up.
*Top surface coat will have the least chemical resistance. While some top coats can be chemical resistant, they will usually not be as forgiving as a blued or phosphate only finish.
*Many final top coats are available, but this also means that there are many that are not as good as others, and therefore their resistance to chemicals, water, wear, and scratches, can vary greatly. Much homework needs to be done before making a final choice of topcoat.