Hunting for 1st pressings

First pressings are often if not always best sounding and worth pursuing.

+1 on last comment by inna. Worth the effort IMO.

As an example. I have Pangaea by Miles Davis on Japanese vinyl, three pressings - original pro, original regular and same year reissue.
There is no doubt that the original regular is better sounding than reissue, and the pro is better still and not by little.
Another interesting example comparing original American and original Japanese. Bitches Brew by Miles Davis. They sound somewhat different - the American is a little more raw and edgy and Japanese is quieter and more refined, both are quite dynamic. I listen to both American and Japanese, though Japanese more often.
And the last example. Inner Mounting Flame by Mahavishnu Orchestra. Original Japanese and Japanese first reissue. They sound different, the original is a little more dynamic and the reissue is more refined and a bit laidback. Both great, I listen to the original.

I agree with inna, first pressinigs almost always sound better. I have even come across a few 'well used' first pressings that are astonishingly good after a cleaning.  I almost always seek them out. In my collection, the first pressings are always more dynamic then later ones, especially most reissues..

Norman

Discogs is pretty helpgul for this sort of thing.