Do 45 rpm 12" LPs really sound better than 33 rpm?

@orpheus10 please stop your analogy with jukebox in each post, the OP is talking about "12inch format, not "7 inch.

What you’re talking about is just a "7 inch SINGLE invented by RCA long before the first "12 inch single appeared on the market.

Every radiostation played singles (one song per side) back then, also every club deejay played singles. This is professional format to promote hits, but please keep in mind that many small independent record labels never released any LPs (just 45s), some of them are private press. It was just a handy format to sell music. Special Promo Singles also pressed prior to LPs (if they were any) to promote new music.

In Jamaica they pressed only "7 inch singles (45s) for example.

Jukebox is just a player in public places for already well known music.

But to make a hit they need a radio dj and promo 45s (singles) to break the record before it became a hit. Same about local discoteques back in the days (in the 70’s).

Music released on "7 inch single is often different version, different take of what they released later on LPs.

Later when "12 inch 45rpm single was invented that was extended version of the song, often different take, sometimes absolutelty unique version available only on single and not available on LP. There was a maxi single format as well with many different versions of the same tune.

This is a whole different culture, compared to what a typical modern audiophile pressing company is doing now. What they do is just a regular LP (originally pressed on 33rpm), but re-issued on 2 x 45rpm "12inch LPs for better quality. Sometimes re-mastered in half speed. But it’s the same music as on the regular LP.

The culture behind the "7 inch 45s and "12 inch 45rpm singles (or maxi singles) is a whole different story. This is not about speed or size, it’s about different version, extended version, different take or remix. This is what makes those records unique, not just different speed or rotation on turntable.

I'm glad most people agreed with Mike Lavigne, even though I said it first.  I don't care if Mike gets the credit; Mike is good company in a discussion of this sort, because he has heard more "stuff", both software and hardware, than most any of us amateurs.

More dynamics. Better by a large margin than LP. When I was heavily into vinyl I would only buy Japanese pressing and also any 12” 45 rpm versions or singles of my favourite hits. Living in Canada our vinyl quality was garbage. Imports is what most serious Canadian collectors bought. Germans may have fared better with local quality but Canadians got garbage quality vinyl. 

@daveyf 
There has been a lot of discussion about the MM reissues (either in 2x45rpm or 33.3rpm) versus the RVG originals. The issue will never be resolved, because they are sonically so far removed it's almost like comparing different recordings.

I always seem to get the impression that the MM's are more faithful to what's actually on the master tape, although I obviously never heard or will ever hear what's on those tapes. The MM's sound incredibly clean and free of distortion, while still having realistic dynamic punch. This is often how people describe master tape sound and each time I hear one I think it can't get any better.

But all that sanity is thrown out the window the moment the needle hits an original. Yes, these records were cut 'hot'. They're very loud and can be a bit uncivilized, sometimes harsh and even shouty. I can imagine this being too much for a high efficiency horn based system. But in terms of sheer exitement nothing really compares.

Oh, and top grade NM copies of the originals are not really noisier than modern vinyl. But finding such copies has become almost impossible, unless you're prepared to pay a small fortune. Actually, in my experience even 'well used' copies can still sound quite good, try that with 'modern' vinyl. Thanks to the loud cut the music will easily overpower any surface noise.