WC - Yu-Gi-Oh! World Championship 2007
SC - Yu-Gi-Oh! Spirit Caller
I guess the fancy quote "Newer version of stuff always beat old stuff" applies to Yu-Gi-Oh! World Championship 2007 over Yu-Gi-Oh! Spirit Caller. For those who doesn't know, Yu-Gi-Oh! Spirit Caller is the first debut of Yu-Gi-Oh! game for Nintendo DS. As we all know, the first debut doesn't always sounds too good, at least not as best as the sequel eh?
Unlike Mario & Luigi: SuperStar Saga (first sequel of mario & luigi co-op game for GBA which many people claims that it's a game far more better than the second sequel for NDS - Mario & Luigi: Partners in Time (second sequel for NDS), Yu-Gi-Oh! World Championship 2007 seems to prove just the opposite thing. In fact, in the latest addition for the game, many cards had been added and as you may recalled Yu-Gi-Oh! World Championship 2006 for GBA which is a non-RPY style game, compared to Yu-Gi-Oh! Spirit Caller.
The battle mechanics and graphic still applies the same for both game - The summoned monsters will appeared in 3D (although it's not well-rendered, it's still nice looking) and the blasting, slashing battle scene still the same. Don't misunderstanding here, you won't see the monsters battling each other as seen on TV anime. Instead, the only thing you'll see is two cards, both left and right, and the blasting (usually dragon, demon), slashing (warrior of course, bugs) graphic scene are done when you're being attacked or attacking other monsters cards. You can't expect to see those monsters attacking sprites would you? Consider the fact that NDS doesn't equipped with high-end 3D graphic card or what-so-ever. Even if Konami did consider to implement the battling sprites for the game, it would take up many space as the game normally would, 1 or 2 GB perhaps?
Nevertheless, WC is definitely a better choice than SC for most Yu-Gi-Oh! fans. The main reason is probably the elimination of RPG style game (SC) which required the user to search and pinpoint any nearby enemies to initiate a battle. As in WC, your opponent is pretty straight forward for you to choose. Just select 'Free Duel' from the main menu, select an opponent (consisting of monsters and humans) then battle. Frankly I couldn't figured how on the earth does a monster duel you? Choosing their card with their tiny or fat fingers than you could barely imagine it would be true. Anyways, each enemies own a deck that are appropriate for their look and their deck name. For example, for a fire fox, it will use deck that mostly consist of Fire type monsters and so on.
The password features doesn't really work in the same mechanic as the GBA version of Yu-Gi-Oh! game. If you think you can just input the password for the card (you'll probably get those password via GameFaq just as I did) and use them in the early battle to gain easy victory, then I'm afraid you're wrong. In WC (I haven't tested the password features with SC yet, sorry), even though you had entered the correct password for a card, let's say 72302403 for [Sword of Revealing Light], you still can't get it unless you had at least one card with the same name or unlocked a packlist that contained the card. Other than that, I'm afraid you just can't get it.
As you may recalled a features in all Yu-Gi-Oh! game - Forbidden card, it's still apply the same in WC and SC. In this time, the forbidden card number just grow larger and larger. You might think it's bad eh? No more Raigeki, Pot of Greed... However, if you think in other perspective, neither you or your opponent can use it! So you can turn this as your advantage. No more need to fear your opponent for using Raigeki upon your monsters.
For me, I really isn't a Yu-Gi-Oh! fans as I seldom play the card game with my friends. However, it's really worth to play if you have got plenty of free time to spent.