My Elitist (on left) compares favorably with my Gibsons.
The Nitro VS Poly is argument is more marketing than facts.
The type of finish on a solid body guitar is a very small part of the overall equation. The thickness of the finish matters more than the type of finish. Thin finishes are the key.
The finish type is more important on acoustic guitars where the sound board vibrates, generating sound. Than it is on solid bodies.
Fender has been base coating their guitars with Fullerplast since 63.
And there are plenty of great sounding Fenders with Nitro sprayed over a "plastic" sealer coat.
Judge guitars on their actual merits. Don't write off a guitar because of the type of finish used.
There are great and crappy guitars with nitro finishes and the same goes for polyurethane and polyester.
One specific element does not make or break a guitar.
Unless you are a victim of marketing hype, overriding your ears.
A guitar is a sum of the parts.
What about this twist?
If a guitar is great and the moisture content is right on, does the poly lock in the guitar to a consistent humidity, consistantly retaining the good sound?
Where if nitro "breathes" the moisture content can vary in the wood, and so can the sound.
Murky when humid, bright in the winter?
Advantages/disadvantages, I guess it is all in how you look at it.
I prefer to differ to my ears on the matter. My ears say that a good guitar can come in many types of finishes.
If the finish really makes such a big difference, why are not all guitars "French Pollished"? It is a time tested finish that can be considered better than nitro for musical instruments.
YMMV