Glad I found this post, I think I can help:
I own all of the Sega CD consoles, the best one for longevity is going to be the model 2.
Sega CDX - if you have the means, this is the sexiest way to play either Genesis or Sega CD games. I always find it amazing at how much smaller it is than the other combo Sega CD options. The laser inside is just okay at reading through scratches and errors, probably the weakest of the models, but it is such a nice system to own. Technical: I own one (from my thrift store days) never serviced and two others I rescued from the grave with new lasers and pot adjustments (and springs, etc.). Not that easy to work on, but better than the model 1. Replacement lasers are easy to find. A few select games are incompatible, but my 'The Terminator' seemed fine on it.
Model 1 - I just rebuilt one and these are very complicated inside, all related to the CD drawer mechanisms. There are three limit kill switches inside, a belt that needs to be replaced, and generally a lot of failure points. Technical: I own two complete units, one never serviced (!) and one with parts from the best of two units. The parts unit had leaky caps on the main logic board that had eaten through some surface mount traces. Unless you have the technical urge and parts units, avoid. A plus: The lasers are of good quality and can read though scratches and errors above average. My rebuilt unit still makes an odd noise, related to a dirty limit switch (I think) that is going to take a lot of complex disassembly to even start to diagnose. It is getting much better with use....use it or lose it I guess.
Model 2 - the most reliable of the units. I have several, two of them upgraded to boxed, all have never needed service. The lasers inside are of average quality, about like the Sega CDX. Average ability to read through errors and scratches. You might get lucky: one unit out of many had way above average error correction and was internally very different from the rest. No one has done a comparison of the internal compoinents inside that I know about.
JVC X'Eye - I have one, and have seen others with weird problems. The first one I dragged home had some odd graphic glitch in Genesis games, others have lid problems. My unit has been fine. Plays imports without modification (hello Super Fantasy Zone!). JP music in the custom Sega CD bios. Should come with a JVC branded 3 button controller, custom power supply, custom RF adapter. Technical: Loads games faster than any other Sega CD. At its best, I would say almost a third faster! Mine is still unserviced, so I suppose if you get a good one...
I hope this helps! Collecting real Sega CD games has just about driven me mad. These were never respected, so it was not uncommon for me to go through several expensive discs to find one good one that did not have pinholes of light. The discs do not hold up to wear at all and should be kept in their cases when not played. If a scratch or pinhole is in an FMV sequence, the game will often crash. Pinholes are okay in music sequences, however. Laser calibration is an issue, since these were all done with pots. I can have a disc that locks up in a Sega CDX but plays fine in a model 2. Given all of this, the Sega CD still ranks among my favorite consoles ever. It was true luxury good that I only experienced a few times prior to picking one up in 1997 in a local thrift store. Get to know a shop owner with a good resurfacing machine, it is a must! I also threw away all of the foam blocks that tend to come with more cared for copies of the games. The foam has degraded over 20 years and had started to stick to the discs. Since they are so fragile, better safe than sorry (no damage, thankfully).
