I have a pair of Pioneer Elite DV-F07 players. Each holds 300 (plus 1, total 301) CDs or DVDs, and one unit can be "slaved" to the other to give you unified control over 602 disks.
I almost bought some large Denon units a few years back that were even better: they held a few hundred disks each, but had TWO play drives in each, and were controlled either by one unit with a built-in controller, or computer controlled via software, or by a remote. They are/were used in radio broadcast studios. Much uglier than the Pioneers, but you could also chain five or six of them together, and they were built like battleships, with excellent (broadcast quality) sound, and because of the two heads in each unit, they offered almost instantaneous switching from one track to the next. Single-head units always have a delay while one disk is being traded for another.
I also have a Technics 100-disc changer that is quite decent, although shifting disks on it is a slower and noiser process than on the Pioneers. I got this one first, mostly for my wife's use, and although the disk-shifting routine never bothered me initially, when I later got the Pioneers, I found the rapid and quiet disk changing on them to be "a breath of fresh air".
That's the limit of my experience with these things. None of the ones I've mentioned are/were disappointments, but each of them has its own strengths and weaknesses. as mentioned.