I'm hopeful they will carry slightly different meanings in the future, where "card sharp" isn't pejorative but "card shark" is. Actually, today is the first time I've heard the term "card shark". Ahhh, English...
I suspect card shark has bled over from loan shark or some other term like that
I think that term (shark vs. the original sharp) got popular due to a TV game show by the name "Card Sharks".
Yes smart bettors call themselves "sharps" and "AP"s (advantage players) I don't think I have ever heard an AP call themselves a card shark. This seems to be a piece of fiction as most of the terminology doesn't line up and the tactics are odd too.
I think I've only ever heard "card shark" used to refer to a person who is really into the game, plays it competitively, and generally knows the probabilities of various hands, but generally isn't counting cards or otherwise keeping track of any hidden game state. They're also generally into betting strategy, bluffing, reading people's faces, and other such things. I don't think I've ever heard it used to refer to someone playing to win by counting cards, except in case where card counter is mistaken for the above.
I've always thought of "card shark" as a common American mishearing of the correct phrase "card sharp." Like saying "mute point" instead of the correct "moot point" or "take a different tact" for the correct "take a different tack."