Which is better: a Chi or a Sedu for straightening long, thick hair?

My wife wants a hair straightener. She has long hair that is kind of straight (not curly), but very thick. I've read that for longer and thicker, you want a wider iron. Chi makes a 2 inch wide iron. Sedu makes one that is comparable in price and has an adjustable temperature control, but it is only 1.5 inches wide. Which one is going to yield better results and be quicker to use?