Cards in mint condition, meaning they have no visible wear or damage, are worth more than cards with minor imperfections
Its also a great sweeper, taking out indestructible menaces like Toski, Bearer of Secrets as easily as soldier tokens
Against many decks you will not be looking to attack much, often having just one attack on the final turn
Less historical data as a newer service, CGC doesnt have the decades of hobby presence or the massive population report that PSA and BGS have (although they are quickly accumulating a large database of graded Pokemon cards)
By Role in the Game: There are three basic roles Pokmon cards (the creatures you battle with), Trainer cards (which give you items, abilities, or effects), and Energy cards (used to power attacks and moves)