I'm pretty sure the stock/finish/cut of all Theory11 decks are the same. So it really comes down to whatever designs you like. The Monarchs are one of my favorite decks ever but I'll also say that the NPH deck carries some interesting secrets. If you like puzzles, you'll like the deck. However, I do think their decks are more geared toward magicians than cardists.
Ellusionists decks are also directed toward magicians as well but a lot of them would look good in cardistry.
I'm not into cardistry so I'm sort of under the impression that cardistry decks were usually more brightly colored, minimalist, and tend to be borderless. That's just me though. Like Magic Orthodoxy said, it's really up to you.
Even though I don't do cardistry, I l0ve the designs of some more cardistry centered decks. Here are a few I like from outside
T11 and
E:
The Virts are classic:
https://www.thevirts.com/fw17/
Dan and Dave have some good ones:
https://www.artofplay.com/collections/playing-cards
NOCs are great for cardistry and magic imo:
https://www.houseofplayingcards.com/
The Orbit decks are great too. Their site doesn't have them anymore but I think Ellusionist still has some stock of them:
https://www.ellusionist.com/orbit-v5.html
Cartamundi recently produced a deck for Cardists:
https://copag310.com/products
Once again, most of these decks are printed by the USPCC so the difference in feeling between them will be minimal. It all comes down to whatever deck designs you like. If you like the Monarch or NPH deck designs, go for it! You do you man