Online Play: Modern warfare 2 or Left 4 dead 2?

Hi guys, I got money just to buy one, which is better? Thinking in online play...

I preffer tatical shooters but everyone is saying that left2 is freaking better than the first one...

What do you think?

Thnx for the help!

L4D2

I like both games but I would say that Modern Warfare has more options but L4D2 is more fun.

My vote goes to L4D2

L4D 2

I have both and I'd say L4D2. It allows for user made comment too, so it has longer legs.

I have both, and I would much rather spend my time playing MW2.