How much does vinyl formulation have an influence on overall sound?

I’m sure it is a factor, based on my listening experience, but combined with so many other variables, from the quality of the original recording, what master is used to cut (and how many generations down), the mastering, and the pressing quality, it is hard to identify how much it makes a difference in overall sonics. That old MoFi formulation from JVC is, to me, one of the best-- very quiet given that it was originally intended for discrete multichannel LPs, though I personally have issues with some of the EQ choices on the old MoFi LPs. On the other hand, pressing plants like Monarch are now valued for their highly visceral, punchy sound. But, those discs tend to be noisy, and that plant was not a high end plant- it was owned by a conglomerate that owned Buddah Records.
Where did these companies get their plastics? Keysor-Century in the US manufactured plastics for records back in the day. I doubt there are any plastics companies that make the resin Stateside anymore-- I believe most of it comes from one large company in Thailand, though the exact formulation can be varied.
I can’t remember who Michael Hobson used for his Clarity formulation- the one that eliminated carbon black in the quest for better sound.
Quiex was another formulation that seemed to be used for promo records and continued in different formulations Quiex II, etc. I suppose they were quieter, but sonically I don’t think that made for a better overall record, given the other factors-
Some of the early Island pink labels in the UK were pressed at Orlake and sound far more visceral than the UK Polygram pressings using the same mastering, which in turn, sound better than the later UK EMI pressed ones (Island switched from Philips-Polydor to EMI at some point in the late pink label era, and most of the pink rims are EMI pressed records). The Orlakes are noisier than either the Philips or the EMI pressings, but sound better if you find an unmolested copy. I have no idea where the plastic was sourced among these different UK manufacturers. I do know that a lot of record people opted for Japanese pressings 3 plus decades ago in the quest for a better, quieter surface, but again, the EQ is not always to my taste. I think part of it depends on the music you are looking for; a lot of the really heavy ticket old prog was reissued by King Records in Japan and those aren’t just cheaper than the original Italian pressings, but have better surfaces.
I’m not saying it’s unimportant, but choosing records based on vinyl formulation is going to leave you in a very narrow corridor. And sometimes, the sonics of an otherwise noisy piece of plastic are going to outweigh a quiet piece of vinyl.
humbly,
bill hart

The quietest pressings we've seen have come from QRP which is owned by Acoustic Sounds.
Its not the vinyl though- its how the pressing machines are damped so as not to shake or vibrate as the vinyl is being pressed.
In mastering different projects that went to different plants, what we've seen is that the mastering quality has more to do with the final sound than the pressing plant. For example, United has a mastering operation, which sounds rather flat and its not unusual to get some surface noise. But if a different mastering house is use and United is only used to press the LP, the results are pretty good. In all our projects we've mastered, no pressing plant so far has indicated any other options other than thickness.

Also the quality of the vinyl and the method in which it is stamped determines whether there will be sporadic drop outs and noise (chunks, potholes, pits) in the groove walls. Some of this depends on the formulation of the vinyl compound, whether it contains recycled materials, etc. Even with a given formulation, there will be batch variation of the quality of the premelted pellets from the supplier. I have several pressings that, except for a few sections that sounds like tearing of the record, they are otherwise quiet and decent sounding.