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

Perhaps there's a valid comparison to tape machines operating at different speeds. Higher tape speed means more 'headroom', as in more length of tape to enscribe the same signal. Likewise on vinyl  higher speed rotation and more space between the grooves means better dynamics. This usually results in more output, which subjectively sounds better if you don't compensate the volume setting. But I'm not entirely sure this really does translate to better sound quality at the exact same volume level.

To escape more inconclusive anecdotes, it might be interesting to compare the Music Matters Blue Note reissues. Their first series were on 2x45rpm, their recent issues are back to 33.3rpm. It seems reasonable to assume they initially made this choice in order to get as close as possible to the huge dynamics that the originals were famous for. It makes you wonder why they went back to 33.3rpm, but this may have been just a way to reduce cost.

I have a few titles, but not the same titles on both speeds. So I haven't been able to make a direct comparison myself. But with use of the same master tapes and mastering engineers on both these series, the comparison might yield more conclusive results.

For what it's worth, to my ears the 2x45rpm titles I own do NOT sound more dynamic than the ones I have on 33.3rpm. In this respect nothing compares to RVG's originals.

@daveyf 
I was typing while you made your comments. So you did make the 2x45rpm versus 33.3rpm comparison of the MM reissues. Results are again inconclusive as they changed their hardware to master the 33.3 version. I didn't know this, so my suggested 'controlled comparison' was based on an illusion. My bad.

@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.