I’m a poker dealer, we use plastic cards, which those are.
From what I’ve heard, KEM went out of business and the cards were unavailable for a long time. The first batches of cards we got from the folks that reopened KEM were horrible. Double printed, etc. Now, bear in mind, I’m just a dealer, I don’t know what kind of decisions they use to purchase cards. For all I know, they buy remainders, rejects or whatever.
In our environment, a deck of cards will show its weakness very quickly. They can bow, split, fade, etc. The current batch we use are pretty shabby. However, I have an “older” generation KEM deck that was used in the room that is in MUCH better shape than the ones I have to use every day.
I’ve never heard of COPAG.
Totally plastic cards are worth their weight in gold. I sent a deck with one of our customers who was heading to Iraq. Sweat, sun, sand, yeah, paper cards or even plastic coated wouldn’t stand up very well there. I’ve run my deck through the dishwasher. A good quality plastic deck will/can take more abuse than you can think about giving it. (Unless you run a card room and have it deal 28 hands an hour, 12 hours a day, 364 days a year)
I’m sorry I can’t say “this brand is best.” However, make sure they are plastic, not plastic coated and you will still be ahead of the game.
(FWIW, blackjack uses paper cards because they switch them out so much, we get new decks maybe once a year or so, depending on how crappy the last batch was)