Kel-Tec has bad and good designs. RDB, Sub2k and RFB - these are good from most ppl experience and I personally had experience with first two. You're correct that you need to be original purchaser so you could use warranty because yeah, things happen and these are not military designes proven by decades and backed up by tons of spare part and wisdom of fan base.
Speaking about RDB specifically. Design is much more advanced than X95. It is more simple, easier to manufacture, less parts to break, easier to take down and get access and clean all parts. At the same time it's boutique type of firearm with a lot of stupid screws (X95 is much worse!) and it's hard to clear malfunction and hard to demonstrate empty chamber, latter two items are important when you compete.
X95 is a generation behind, with so many stupid design implementations. But... it is high quality firearm based on military issue design and it just works. Hard so service, but it works even with little service.
I sold my RDB and I kept X95. I hate bullpups, I hate outdated and outright stupid design of X95, but beggars can't be choosers. I know I can rely on X95 in both CQB competition and zombie hunt. I also sold Bren 2, but that's another story. If I were you I would have bought used X95, honestly, though I loved my RDB. It was sub-MOA with heavy bullets as opposed to 2.5ish MOA of my X95. If not competition and zombies consideration I would rather kept RDB. So, act according to your priorities. If it's only plinking - grab RDB, if you value more robust design and don't mind some hassle when cleaning - grab used X95.