On cooling: Asus takes the cake for me. I've never owned an Alienware, but two friends have.
On audio: Doesn't matter. Alienware might have better speakers and amplification => better sound quality. However, when I game on my laptop, I use headphones anyway, so I don't care about the laptop speakers even slightly.
On design: Alienware design (absolutely every Alienware machine - every one) looks ridiculous and gaudy compared to the sleek, elegant design of most Asus products. My favorite is, so far, the G55vw - I don't care for the design changes that were made in the G75 series.
On price: Myk covered it completely.
On hardware: Before purchasing my Asus laptop, I looked to competitors for the best hardware vs. price. I bought an Asus laptop.
Z
Edit: On a side note, your question seems a little silly, as this is an Asus owners' forum.
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