I’ve always observed 45 provides a noticeable increase in quality, even for crap lo-fi stuff. I’ve got some 80s singles and I once tested this, with a 12” 33, a 7” 45, and a 12” 45, all of the same track. The 45s both sounded way better. The 7” 45 I used must have been played more than the 12” 45, or else it wore faster. The 12” 45 sounded light years better than the 12” 33.
—Daniel Deathtide