pick whichever makes the most sense for you. If you plan to get a new laptop next year, then one year is fine. If you are going to keep that machine for a while then you might want to get a longer warranty...it's just an insurance policy incase something goes wrong. Get the one that makes the most sense for you financially and in terms of security. Two years was the sweet spot for me because I figure I'll get a new machine after two years.
Also, you seem new to Alienware and are definately new to NBF, so Welcome to both. We're glad to have ya'.