Seeming no one really answered your original question on the main differences between Colleseum and XD here you are.
Poké Spot is a new feature in Pokémon XD that was not included in Pokémon Colosseum. It allows players to battle and capture wild Pokémon. There are three different PokéSpot areas: Cave, Rock, and Oasis. Each spot has different Pokémon that might appear. They also have Pokémon that are rare to them, those Pokémon can be traded ingame. To get a Pokémon at Poké Spots, however, one needs to encourage it there with food, called Poké Snacks, a bit like Pokémon Ruby and Sapphire and Emerald's Safari Zone Poké Block feeders. But, you will not always find a wild Pokémon when you lure a Pokémon there, as you could find a Munchlax at the Poké Spot.
Shadow moves
Shadow Pokémon are only able to use Shadow moves until they begin the purifciation process; this happens after the player has captured them. In Pokémon Colosseum, the only shadow move is Shadow Rush; this has been expanded for XD. There are now eighteen Shadow attacks. Shadow moves are "super-effective" against non-Shadow Pokémon but "not very effective" on Shadow Pokémon. A complete list of shadow moves: Shadow rush, shadow blitz, shadow wave, shadow rave, shadow half, shadow sky, shadow mist, shadow shed, shadow hold, shadow panic, shadow storm, shadow down, shadow break, shadow end, shadow chill, shadow bolt, shadow fire and shadow blast.
Shadow Pokémon
Pokémon Colosseum contains 48 Shadow Pokémon. This game features nearly double that, 83 Shadow Pokémon. Trainers that previously only had one Snag Pokémon now have two. Most Cipher Admins may have up to three Shadow Pokémon; Cipher Admin Eldes has four. The last boss, Grand Master Greevil, has a full party of Shadow Pokémon.
The 85 Shadow Pokémon featured in this game are: Teddiursa, Ledyba, Poochyena, Houndour, Spheal, Mareep, Gulpin, Baltoy, Seedot, Numel, Spinarak, Carvanha, Shroomish, Delcatty, Makuhita, Voltorb, Ralts, Duskull, Vulpix, Mawile, Pineco, Snorunt, Natu, Roselia, Meowth, Swinub, Grimer, Seel, Spearow, Lunatone, Zangoose, Nosepass, Togepi, Paras, Shellder, Growlithe, Pidgeotto, Beedrill, Tangela, Butterfree, Magneton, Venomoth, Weepinbell, Arbok, Hypno, Primeape, Raticate, Sableye, Farfetch'd, Golduck, Dodrio, Altaria, Kangaskhan, Banette, Magmar, Pinsir, Magcargo, Rapidash, Lickitung, Hitmonlee, Hitmonchan, Scyther, Chansey, Starmie, Solrock, Swellow, Snorlax, Poliwrath, Dugtrio, Mr. Mime, Salamence, Manectric, Marowak, Electabuzz, Lapras, Articuno, Zapdos, Moltres, Tauros, Rhydon, Exeggutor, Dragonite, and Lugia.
Purify Chamber
In Colosseum, Shadow Pokémon were purified one at a time at the Agate Shrine. However, since this game features many more Shadow Pokémon, the Purify Chamber was created. In it, a Shadow Pokémon is placed in the center of a circle and up to four regular (non-Shadow) Pokémon are placed on the circle. The regular Pokémon lead and open up the Shadow Pokémon's heart. The Purify Chamber can purify up to nine Shadow Pokémon at once, each in their set of four regulars and one shadow.
Battle Sims
After receiving the Disc Case from the Cipher Peon disguised as a lady at the gates of Phenac City, you can play them at Realgam Tower. You find through Orre many Battle CDs to use for the Battle Sims. Battle CDs are pre-programmed battles with different rental Pokémon. Some battles have restrictions, such as how many turns players can take and any preset status conditions. Completion of a Battle CD the first time earns an item as a reward, ranging from a Super Potion to a Sacred Ash.
Battle Bingo
Battle Bingo is another mini-game found at Realgam Tower. The goal is to clear a 4x4 grid with using some Pokémon in battle. You start by choosing your card, with its own Pokémon. You get to use that Pokémon and 2 master balls. Then choose a square and fight a wild Pokémon of the type stated on the square. If you win, you clear the square and choose another that is ajacent to it. If you are at a type disadvantage or just want to use the wild Pokémon because your running out of EP, you may use a master ball to catch it. Note: you do not get to keep any Pokémon you get in Battle Bingo. If you choose a square with a "?", you get EP, extra master balls, etc. You can also get EP by clearing a line of squares. The game ends if you win or run out of EP. The player can also obtain a Bonsly card after finding the lost Bonsly which can be used to unlock a new Bingo card that allows Bonsly to be the starting Pokémon for Bingo. This is the first time in Pokémon that Bonsly is a usable Pokémon in battle.
Quick Battle
Quick Battle was also featured in Pokémon Colosseum. In Quick Battle (which is selected by selecting "VS MODE" out of that, "NEW GAME," and "CONTINUE.") you can quickly battle a friend with Pokémon that you may not actually have in Story Mode. (In Pokémon Colosseum, you can only battle a CPU.) The Pokémon in Quick Battle also have more creative movesets than in Colosseum's Quick Battle Mode, such as Pikachu knowing Dynamicpunch as well as other rare moves. Moves are now selected with the C-Stick instead of the normal selecting system. The final and probably most noticable change to it is that it is always a double battle and teams always have 2 Pokémon.
~Kipper~
