Any advice on where and which Sega Saturn to buy that would be a reliable? I have a white Japanese one that even after replacing the laser routinely doesn't read discs. My OG black US one reads some games, but then stops after playing for a while. I have an action replay 4mb cart, which functions well.
I'm happy to buy again from Japan, but I'm unsure of who on ebay is a reliable buyer, and which model would be my best bet. Still can't beat Panzer Dragoon Saga because my Saturn crapped out. Feels silly to own it but not beat it.
Any advice appreciated!
Sadly, as these systems age, it's going to be harder and harder to find one that just works. Many of them are getting to the point where they need some sort of servicing. This is especially true with the CD and DVD based systems since optical drives can be unreliable.
One of the most basic things to do is to at least ensure the CD drive's lens is clean. You can either use a cotton swab with some 91% (or higher) isopropyl alcohol or one of those special lens cleaning discs (or both). Cleaning and regreasing the rails that the laser mechanism rides on can also help alleviate disc reading issues.
The next thing to consider is old capacitors. As they age, they're more likely to fail and cause all sorts of issues (including reading discs). This isn't that difficult to do yourself if you have the equipment and knowledge, but it's something most systems will need at some point.
Even if you buy another one that works great now, you may be back where you started in a few years. It's really hard to tell with consoles that are this old. It may be better (and possibly even cheaper) to see about servicing your current Saturns.
Now going to your specific case, the white Saturns were Model 2s. They were pretty similar to Model 1s in terms of general reliability, but they did have compatibility issues with just a couple of games. If it's not those games that its having difficulty reading, then the next thing to check would be the optical drive, but you said you've already replaced it with (what I assume is) a known working drive. If that's the case, then it might not have anything to do with the drive itself and capacitors would be the next thing to check. You may not even need to recap the whole console, it might just be the ones in the power supply that have gone bad like Saoshyant said. I'd recommend trying to repair the power supply before replacing it with an third party one though.
If your US Model 1 is having problems reading discs and the discs themselves are fine, then it could be the same situation. I recapped the power supply and main board of my own Model 1 and it improved the disc reading significantly. I had one disc that was heavily scratched--including damage on the label side--wouldn't play at all. After the recap it would play everytime. I then tested it on another Model 1 that still had the original capacitors and it was failing to load just like on the other Saturn.