The original PGI china clay chips (produced on the greek key "reverse-L" mold) had 4d14 spots (or solids with no spots), and later, 8V spots. Those chips seem to be a different mix of materials than the more recent PGI CPS chips (Championship Poker Series, on the tower & spear mold), although they were produced by the same manufacturer with raw materials supplied by PGI. The earlier chips seem to contain more 'earth' materials (silica, etc.) and less synthetics (plastics), and as such, have a more chalky appearance, feel, and sound. However, even the tower & spear mold chips (with cross-hatching) seem to be more "earthy" than other recently produced china clay chips commissioned by ApachePokerchips, such as the Majestics and new Dunes -- both of which appear to be have a much higher 'plastic' content than all previous china clays.
The other "big three" china clay chips (Pharaoh's Club, Desert Palms, and the original Dunes Commemorative chips, each with their own distinctive mold) were commissioned by TheChipRoom and also have an 'earthy' feel, although not to the same degree as the early PGI commissioned chips. This is also true of other early china clay chip chips, which were produced on the spirit mold by Eastony Industries (several spotted and no-spot versions of blanks, plus the 8D14-spotted Pyramid Casino and Casino da Vinci lines that were commissioned and sold by Da Vinci and later other online vendors). It is less true of the greek key (reverse-J) mold sold as ProGen 80.
Non-PGI china clay chips use materials at the discretion of the manufacturer (i.e., materials not supplied by PGI). One of the reasons PGI always supplied raw materials is because the factory otherwise typically included recycled materials in the chip formuula, which PGI felt were substandard. There is definitely a difference in the way PGI supplied chips sound, stack, shuffle, and feel compared to all other china clay chips. Durability is another issue altogether.... as the more 'plastic' and less 'earthy' a china clay chip is, the less likely it is to break, chip, or disintegrate. I think it's too early to tell about the long-term durability of the most recent offerings (CPS, Majestic, and new Dunes).
All china clay chips are injection-molded and have adhesive-backed stickers (not inlays), regardless of what you read on CT. Produced using pressure? Yes. With heat? Of course. But there's no compression (beyond the pressures of injecting the molten plastic mix into the mold), at least not in the same sense as the true compression-molded processes used by Paulson, BCC, and ASM/CPC.