I have one of each of these 3 non-IDE interface 2x drives, all are working fine and read CD-Rs somewhat reliably. This is my experience with each of them:
Sony CDU-31A
I got this one along with a CT1690 SBPro 2, they were probably bundled as part of an early multimedia kit since the card has a sticker on the back that says "CDU-31A" and they both have december 1992 datecodes. The drive was not working when I got it, by opening it I immediately noticed the problem: leaking SMD electrolytics, every single one of them had failed and replacing them brought the drive back to life. I also had to reflow the power connector since it had broken joints.
As far as I understand, the cap problem is quite common with this model and the CDU-33A as well, so if you want one of these working you will probably have to do a recap. Personally I haven't had a problem with the unusual eject mechanism.
Panasonic CR-563-B
This one was also non-functional when I got it, and this model also seems to have a frequent problem: a small plastic gear that is plugged into one of the metal rods breaks down and becomes loose in the shaft, which prevents the laser from moving properly. Luckily, this is the same drive used by the Panasonic 3DO so you can find good quality 3D printed gear replacements on eBay and the fix is quite simple.
Of all three, this drive seems like the flimsiest one due to how the laser assembly was constructed.
Mitsumi FX-001D
This one was the only of the three drives that I got in working condition and it still works fine to this day so I say get one of these if you don't want to have repairs to do. Not many negative things about it, although I seem to recall it has some foam around the case to prevent vibrations and it can disintegrate with time, so you may want to look into this as well.