Re: Finish types?
Poly is a more durable finish that will take more abuse while staying "good" looking for longer. If it is applied well, it can look out of sight when it is brand new (e.g. G&Ls), but it wears differently than lacquer (less attractively, IMO). Instead of wearing down bit by bit in a smooth fashion like lacquer, it pretty much resists any gradual wear from friction alone. But it slowly becomes covered in tiny pits, hard-edged chips, and sharp scratches, due to impacts. Then those little cracks and dents will keep their hard edges and fill with dirt and grime and look darker. With lacquer, the finish will actually rub off bit by bit over the years even without damage, just from the friction and oils from your body or clothes. And the damaged areas end up being more smooth around the edges in the end. I also find that the chips and such are easier to keep clean, and that scratches are easier to disguise.
Because of all this, I'd say that if you want your finish to stay looking the newest for the longest time, poly is the way to go. If you are extremely careful with your guitar, and don't give it little knocks and nicks, it will stay looking new longer than you will live. But if you want your finish to gradually "break in" in a smooth way, and for damage to be easier to disguise, lacquer is the way to go.
The feel is very different as well. Even the best and thinnest poly finishes are still plastic-like. They feel more like an impenetrable "shell." Not a good or bad thing, just a matter of preference. Lacquer feels more like an extension of the wood itself to me. But flat-finish poly on necks can give a really nice feel that is not all that different feeling than flat-finish lacquer or worn-in gloss lacquer IME.
I don't believe that the type of finish makes much, if any, difference in tone on solid-body instruments. I've heard too many examples of lacquer-finished guitars that are just not good sounding, and too many examples of poly-finished guitars that are great sounding. And vice versa on both counts. I believe the musical qualities of the chunks of wood themselves matter, as well as the pickups and setups, not the finishes. I have even refinished poly instruments in lacquer, both solid body and nylon-stringed acoustic, and could tell no difference in tone – only in feel.
Over all, I prefer lacquer all the way around (gloss), and I will always use it if I have the choice of which to use. However, I am not a lacquer snob enough to think that a poly finish makes a solid-bodied instrument any worse in quality or tone.
