Who can offer you better methods to buy World of Warcraft Cataclysm key

There are several methods to obtain the activation keys require to register World of Warcraft under your battle.net account. Which is "better" would depend on your personal preference and what you currently do to buy your games.

1) Buying from the store - CD version, less download time required, takes travel time.
2) Buying from the blizzard store - download version, immediately available at any time.
3) Buying a CD from an online store - shipped to you, CD version, takes a long time.

Since a key can be used only once, there's no option for obtaining the game second-hand - and trading accounts is not allowed by Blizzard.