That's a good question brother... and the answers you get will vary from person to person, because "good" and "bad" (in terms of how cards feel and handle) is completely subjective. As they say, "one man's food is another man's poison".
I do gambling sleights, rather than cardistry or magic... and so for me, gambling routines like what Richard Turner, Jason England, and Darwin Ortiz do, those are the types I take inspiration from. So I do lots of false dealing, false shuffles, and riffle stacking.
Therefore, I need cards to be traditionally cut -- it makes faro and interlace shuffles so much easier for me.
Given my style of handling cards, I need cards to be pretty stiff, very durable, and also, to be pretty slick... and that is why LPCC's diamond finish (which is the same as EPCC's master finish) is my favourite. What I like about the diamond/master finish coating, is that when I need to extract a card using just a fingertip, the coating has enough grip/tack to it to allow a card to be extracted effortlessly... and yet the cards slide through each other for false shuffles just as beautifully. It's perfect for me.
With USPCC magic finish cards, yeah, they are slick... but due to ridiculously low tack/grip, the first few shuffles with a magic finish deck for me usually result in at least one round of "52 card pickup".
I know that many still like USPCC cards, but they are genuinely terrible for me... because USPCC cards just do not last long. With the shuffle work I do, a USPCC deck becomes good for the trash can in pretty much one or two days. My LPCC and EPCC decks usually last a month.
USPCC cards like the latest Black Lions decks feel more fragile than ever before... and so I don't have confidence in them, knowing that just a few rough shuffles later, the cards will end up having difficult to remove bends in them.
(Having said that though, the White Lions decks by USPCC were very good -- relatively durable, and had nice thickness)
Many magicians swear by Bicycle decks... and the things that make standard Bikes terrible for me, are probably the things that make Bikes perfect for them.
As for design... I like borderless back designs, purely for the fact that they make false deals more difficult to spot.
So to sum it up, a deck with a borderless back design from LPCC/EPCC with diamond/master finish, tends to be perfect for me to do gambling routines.
For MAGIC routines (such as mentalism tricks), there is only one deck I ever use.. and it's one of the few decks I like which doesn't have the diamond/master finish, is the Sharps by LPCC... and that's purely because the marking system (it uses factory shade/juice) is by far the best I have ever come across.
It's the only marking system that passes the riffle test, and the markings are completely invisible to anybody that hasn't trained their eyes to read the patterns. In fact, it's the ONLY marked deck that I'm willing to hand out for inspection, because no matter how hard anybody tries, they won't see the markings!
I think that for magic, having a marked deck which I can read very clearly (and that too from across a table!) is priceless. And the fact that the Sharps have a thick and durable stock, nice coating, and are traditionally cut, is like icing on the cake for me!