I'm inclined to agree that the quality of the player is in the choice of components rather than single disc vs multi-disc but I also agree that a single disc player has fewer parts that can go bad and in general will be more reliable.
I had an Onkyo 6 disc CD changer and it worked reliably for many, many years; in fact it is still in service at my sister/bro-in-law's house. However, multi-disc changers slowly get out of alignment and disc 1 is sometimes not recognized now. The benefit of a multi-disc changer is when you want to load a bunch of discs for 'party mode' but there are so many alternatives now with streaming audio devices that that feature is not so important anymore and I would choose a good quality single disc player.
The only advantage I see to multi-disc DVD changers is if you have kids. Anyone with kids knows they will watch the same movie over and over and it's great to be able to load multiple movies at once and easily switch between them for that kind of situation. For adults, I don't see the benefit at all.