gdgt

The A30's are designed for more general use. Basically, you'll use them for gaming on your console, and then take them with you to listen to music and stuff on the way to work, school, etc. For most gamers this is fine -- though I've seen people complain that the A30's have a higher bass response (for music purposes and such), so ambient sounds with a lot of bass can drown out lighter sounds when playing certain games.

The A40's are designed for tournament / competitive gaming and are tuned for a different use case. You won't want to take these things out and about to listen to music or watch movies.

Both are fine for playing games -- but ultimately it depends on how hardcore you are. Want the best sound you can get when gaming (and are willing to pay a bit more)? A40's. Okay with more general purpose headphones? A30's.

I'll disagree with Dave a little here - it's not so much about how hardcore you are. It has a lot more to do with what is more comfortable on your head.

The A40s are an over-the-ear design, where the A30s are an on-the-ear design. The other differences are with the size/quality of the microphone and the A40s have ear pads that you can swap out (similar to many of the mid to high end headphones on the market, like Sennheiser.) I can't recall off-hand if the A40s are a closed or open design - I think it mentions it on the website.

As Dave said, the A40s are a bit bulkier also. The A40s are comfortable, and I like them as well, but the A30s are a great combination of price point and quality.

I got my A30s at PAX back in 2010 and I love them. I use them for gaming, as well as listening to music/watching movies. They don't give me ear fatigue after wearing them for hours, like many other headphones in my past. Adding in the Mixamp makes the sound quality jump a step and the Mixamps have some great team chat functionality if you're into that.