I love my CHI. I have had it for 8 years, and it still works fine. Granted, I don't straighten my hair every day. I bought it from a stylist before they were available through regular stores, so maybe the quality was better? It was definitely expensive, but it was the best $160 I've ever spent. (This from the girl who never spends money on beauty products; I get my hair cut at Great Clips, and then only with the $6.99 coupon!)
I used to say I should do an infomercial for CHI because it is truly miraculous how awesome my hair is with it. I've never used the other brands, so I can't speak to how well they hold up, but this is what sold me on the quality: Initially I bought it for my 10 year HS reunion, and it ended up raining that night. I was in a panic thinking my hair would frizz out, but it held up beautifully. Of course, you can't get soaked, but a little sprinkle won't hurt. :) Good luck deciding!