Acrylic laser cuts well, unlike most other thermoplastics. however i think the discussion was centred more around acrylic tubing, and that tends to get used because people like transparent cylinders, and also you can get it in a wide range of sizes. Polycarbonate is a better alternative, but costs a good deal more. PVC tubing is available transparent, but tends to be very expensive compared with the opaque plumbing stuff, and offers no other advantage.
Datasheets can be a bit misleading, as they tend to give slightly higher compression percentages than we need for models. 15-20% of the o-ring cross section is more than adequate