Oriented - Almost always for A5, and (seems to be) always for A8. The 'grain' in the metal is aligned in one direction when the mag is formed, which makes for a stronger magnet.
Unoriented - Typically for A2, A3, and A4, and rarely A5. The 'grain' in the metal is random which gives a warmer, richer tone. More dynamics in a guitar PU.
Polished - Ground smooth and shiny. Almost all guitar bar magnets are polished. Gives a more uniformly-defined magnetic field, and a slightly sharper tone.
Unpolished - A4's and A8's are sometimes available unpolished, which means partially ground, but still has rough grinder marks. Tone-wise closer to a polished, but maybe a little more complex.
Roughcast - A2, A3, A4, and A5 are sometimes available as roughcast. Lumpy, bumpy, and still has sand indentations. Magnetic field isn't as uniform, and that makes guitar tones more complex and smoother on the high-end.
So, a polished A5 is bright and scooped; a RC A5 is smoother on top with a bit less treble, and an UOA5 is much warmer and fuller, closer to an A2.
A2, A3, and A4 are always unoriented; choose between polished, unpolished, or roughcast, depending on your desired tone.
With A8's you get polished or unpolished, the difference is small, but I prefer unpolished A8's.
We have a lot of magnet choices these days, and prices are low. Great time to tweak your tones and get just what you want.
