Do 180g vinyls sound better or is it a myth ?

I agree with paraneer....I prefer vinyl to CD, and found that my heavier vinyl sounds no better than regular vinyl.  So much is dependent on the production... I have recordings with claims to Nirvana in sound to be clearly inferior to regularly produced records.  Its a crap shoot.

1. Myth if interface of record to platter is good.  Best IMO to look for old records in good condition.

2. It depends mainly on your vinyl system and set-up.

180 gram vinyl gives the listener a feeling that it "might" be better which in the mind of an audiophile means it’s better. It might not sound better…but it’s better anyway…exactly like the break-in period of your cryo treated wall plugs…after 2 months you think they sound better, so that’s better by definition. You simply feel better, and that’s all the better one needs. Plus, 180 gram vinyl LPs have the advantage of using more vinyl in the manufacturing process which keeps all that extra vinyl from going unused. You want globs of gross unused vinyl to pile up next to Little Johnny’s pre school? Choking the life out of Chilean Sea Bass? Sticking to your feet at the  Trump rally? No, you don’t.

Here are my experiences.

When I was 16 I cut out a record by The Archies from the back of a cereal box. I put it on my big brother’s turntable/separates rig to play it for my amusement--as in how awful it would sound. To my surprise it sounded as good as a real pressed record. Go figure. I’m sure with my present rig its shortcomings would be more obvious. But with a record grip holding it down, maybe not.

I have a modest KAB rubber record grip. I find that it lowers surface noise and makes a 70g Dynaflex record sound more like a 140g pressing.

I also got a special Classic Records release of Elgar’s Enigma variations on both 180 and 200g pressings. I figured they’d sound identical, especially with the record grip. To my surprise the 200g really did sound better. Since this was a large scale orchestral production, I suspect that the extra mass helps handle the dynamics and deep bass modulations.

So I don’t know. Maybe the answer is "sometimes." It could be a difference in the mastering of one vs. another edition, and the record weight isn't the issue. Maybe it depends on how dynamic, dense, and complex the recordin. You might hear a difference with a 100-piece orchestra playing a 20th century composition that won’t show up with a 4-piece combo.

I think that everything up to the point of actually stamping the vinyl has way more to do with sound quality than the weight of the vinyl.

Also, the plural of vinyl is vinyl.