(For reference, Yu-Gi-Oh! will be referred to as a Card Game instead of OCG (Official Card Game) or TCG (Trading Card Game), due to international inconsistencies in naming.)
Information on the Card
Both card games have similar presentation on non-monster cards, where only the picture and the effect are visible. However, the monster cards have different presentation. A Pokémon card shows not only the name and picture of the Pokémon, but also a page from its Pokédex entry, its HP, Type, Weakness, Resistance, Ability, attacks it can use (along with possible attack effects), retreat cost, artist name and its evolutionary stage. That’s a lot on one card!
As for a Yu-Gi-Oh! monster card, it has the monster’s name, ATK (attack points), DEF (defense points), Attribute, Type and type of monster card, leaving a larger space for the picture. The card’s color indicates the type of monster card. The most abundant color is orange, the Effect Monster card. Effect Monster cards were rare early on, but are a common sight these days. Normal Monsters are the only monsters that have description text on the monster, because the text on other Monster cards are used to explain the monster’s effects or its summoning requirement.
Both of them have a small number that is unique to every card for identification. Yu-Gi-Oh! uses an 8-digit number, while Pokémon has a unique set symbol along with a number slashed with the total amount of cards the set comes with, which is useful for keeping track on what cards you have.
Bill is helpful once again.
Now, you will often hear that card sets in the Pokémon TCG are rotated out. Meaning that after the card is "rotated out," cards from that set are not allowed due to incompatibility with the new rules. In a way, those cards have “expired.” If the players choose to they can use the Unlimited Format, where players can delve into the TCG’s long history of released cards, although I imagine that some cards will be extremely useful; Bill comes to mind.
However, in Yu-Gi-Oh!, the cards you had in 2003 can still be used, and there’s no expiry date. The only catch is that some cards will have updated wording (due to errata) that will affect their effects, so if the old card were played, the new effect would be used. The downside to this is that some older Yu-Gi-Oh! cards are more expensive than Pokémon cards, and certain trendy Yu-Gi-Oh! cards can be very expensive to get!
Changing of the Ban List
In the history of the Pokémon TCG, there have been only four banned cards: two were banned for being gamebreaking, one was banned because activating its effect is difficult, and another was banned for being unreadable. Other than those, there have never been any banned cards in Pokémon, which, in a way, shows how well the cards are designed.
However, in the Yu-Gi-Oh! Card Game the ban list that changes every March and September. The list shows which cards are Unlimited that were previously restricted (three copies per deck), Semi-Limited (two copies per deck), Limited (one copy per deck) or Forbidden (banned cards). This is important because certain cards can break the game or make the game too fast if players are allowed to use those cards freely. In a way, the purpose of the list is to encourage diverse play styles. There are few players who don’t like to conform to the list, so they play in Traditional Format, which treats every currently Forbidden card as limited, harkening back to the days when strong cards were Limited at most.
Hand Size Limit
In the Pokémon TCG, each player starts off with 7 cards (8 cards after a draw). Whereas, for the Yu-Gi-Oh! Card Game, each player starts off with 5 cards (6 cards after drawing). That explains the start, but is there a card limit from there on out? There is a limit on how many cards you can have in your hand in the Yu-Gi-Oh! Card Game, and you have to discard until you have 6 in your hand at the end of your turn unless effects that change the hand size are active. As for the Pokémon TCG, you don’t have a hand limit, but if you got the cards, you might as well use them because some card effects discourage having a big hand.
A different way to win the game.
The common winning condition in the Pokémon TCG is to collect all the Prize Cards, which can be done by knocking out your opponent’s Pokémon, regardless of whether it’s Active or Benched. Each defeat nets one prize, or two for defeating the stronger Pokémon EX. You can also win if your opponent doesn’t have any Benched Pokémon to replace a defeated Active Pokémon. Your victory can also come from decking out the opponent, meaning they have no more cards in the deck, but you only win if they need to draw. The only alternate winning condition in the game as far as I know is through the usage of the Lost World, in which the player wins if their opponent has six Pokémon in the Lost Zone.
In the Yu-Gi-Oh! Card Game, you can also win by decking out the opponent, but usually players win by causing the opponent’s Life Points to drop to zero, which can be done through either battle or effect. However, this game has more alternate win conditions than the Pokémon TCG, which includes having five pieces of Exodia in hand, lasting twenty turns since the activation of Final Countdown (turns count for both players) and winning a battle through the effect of Last Turn (that card’s now banned, however).