Re: what's the difference?
i think That a seasoned guitar gets worn, the edges of the fretboard get worn, the trem springs get stretched in a bit, but also, any niggles usually get sorted out. If you're going to play a guitar, you want it to play well, so you give it a proper set up, sort out the truss rod, the action, the intonation and so on. Usually you tweak them over a series of setups until they're just right. That coupled with the neck wear means they tend to play better.
Conversely the best playing guitar I've got "straight out of the box" was my JEM10, which is still better than anything else I've ever tried anywhere... so who knows!