45 vs 33.3 RPM

Cutting and playback at 45 rpm can deliver significant sonic improvements in resolution, dynamics and bass response. For an explanation, read the excellent article by mastering engineer Kevin Gray on Why 45 rpm?

I have most of the Classic Records RCA reissues on both 33 rpm and 45 rpm. Listening here, the 45 rpm pressings are consistently and very noticeably better in the areas I mentioned above. And in the case of Classic Records, if I recall correctly, many of the 45 rpm issues were mastered after Bernie Grundman switched his mastering gear to tube electronics as part of the Mercury reissue project. Thus, many of these Classic Records 45s benefit further with improved tonality and rendition of timbre. (I don't know about the Clair de Lune pressing in this latter respect, and haven't listened to it in a while.)

The Music Matters and Analogue Productions 45 rpm jazz reissues that Kevin Gray has been cutting have been phenomenal. While it's often challenging to accommodate classical music on the 10-12 minute sides of a 12" 45 rpm disc, the jazz recordings are well suited to these shorter sides.
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Another factor may be the dynamic range of the original master tape. 45 rpm is definitely capable of better dynamic range, but if the range on the tape is within the limits of 33-1/3, you might not hear much difference with the 45.

Since most audiophile 45s are purposely not grooved as far in toward the spindle, and spin significantly faster at the end of a record than a 33-1/3, one would think that you would be able to tell the difference in the inner groove section of the 33-1/3 vs. the 45.

Rosedanny, 45's like 33 1/3 rd's are not created equal and your observation regarding the lack of discernible difference between the two "Claire de Lune" pressings is not surprising. I had a copy of Classic Records 200 gram 45 rpm release of Norah Jones "come away with me" (notice I used the past tense) and it was inferior in every way to a relatively inexpensive European 33 1/3 pressing. That being said most of the 45's I have sound fantastic and for each of the few I have for which there is a duplicate 33 1/3 LP in my collection, the 45 version does sound superior. There are still, however some really special 33 1/3 that blow away some of my 45's.

I have more 45rpm than 33rpm, I have many of the Analogue Production BlueNote reissues and also the MusicMatter reissues, but my best sounding LPs are all 33rpm.

Perhaps 45rpm is technically superior than 33rpm, but the difference is secondary compare to other major factors such as the quality of master tape, remastering expertise, and quality of pressing.

ironically, the motivation is little more than a second bite of business from the same title. do they always sound superior? if the music contains 'out of this world dynamics' maybe a bit. it does however change the artist's intent, and maybe the listener's experience as well. Most of the classic long players were made to be experienced as just that. Can you imagine the second side of abbey road in two parts? or dark side of the moon carved up, just so an audiophile can claim it improves a couple of bass notes? like any industry...anything worth doing, is worth overdoing. the joke is, in many cases, the labels that do this don't have the money to actually bring the original analogue masters up to par anyway. the 33 and a third long player is still the route to go, provided the production steps are done properly. just more proof that the hobby covets sound more than artists, their creativity or their music......desolation row parts one and two? i don't think so.

In theory 45 rpm should be better, but theory does not always show up in practice. Without doubt the shortened playing time is a nusiance.