For many years, my preferred brand of acrylic was Lucite L because it is a continuously cast product that cut better (with a saw), polished better and seemed to be more scratch resistant than extruded acrylic such as Cyro's FF-3. That was in the days when Lucite was a Dupont product. Dupont put a lot of marketing dollars into branding Lucite and that is why many still request it today. The same goes for Plexi, which is no longer manufactured by Rohm and Haas.
Since they (Dupont) sold out, Lucite is now manufactured by Lucite International, I have found it difficult to get.
It seems that the industry "default" is Cyro's FF product, which is extruded, and I think it has a lower molecular weight, and appears to be softer. Cyro also has a version called, FF-3 or "framer's grade" which is supposed to have closer tolerances on not having "black specks" and comes with a better "warranty" on replacing product that has been cut and then the specks are found as a part of the fitting process. We have been using FF-3 for some time now, have rarely found any defects, but still miss the "old" Lucite-L. In addition, it is hard to get paper masked FF-3 in the sizes we like, so we are stuck with film masked. The film is easier to get off, but tougher to work with if you are fabricating.
I find that continuously cast product is "flatter" and at .118 tends to bow less. With FF-3 we won't use anything thinner than .118 becasue on larger sizes it tends to "pillow" in the frame under its own weight.