You can read about the two brands at:
Lots of people say the difference is “Coke and Pepsi,” just personal
preference. For the main products, they are very similar. Both
offer clays that fire at the same temp, paste/slip, and pre-loaded
into a syringe. Art Clay also has Slow Dry, which takes two hours
to dry and that lets you do things like braid with it. And they
have Oil Paste, which is for repairs and I’m not sure what else.
PMC has sheet, or paper, which is rubbery in consistency and doesn’t
stick to itself. It was created for origami, but there are lots of
other fun things to use it for.
You should know that you can’t mix the two products together, or you
will get irregular shrinkage.
Each brand offers it’s own teacher training programs.
Chicago area, Illinois, USA
Metalsmith, Certified PMC Instructor
Studio 925; established 1992