Jackson's Art is better. Cassart prices are often very inflated (a lot higher than Jackson's Art or Bromleys in the UK) and their online store uses the worst delivery service (Evri) which have lost two packages, and damaged more. Unfortuately there isn't an online order I've made from CassArt that did not have a problem. The two standing stars are for the in person stores which are nice.

If you do shop in person at CassArt, I recommend checking Jackson's Art and showing their price at the till so that CassArt can match it.