AirAsia is really shitty. The only redeeming quality is that it's cheap. There's barely any leg room, and a minimum of 80% of people on their flights are low class. Loud mainland Chinese people yelling about what I imagine is utter nonsense. As other posters have said, AA will nickel and dime you for everything.. they charge extra for food and to check in bags. You'll also be arriving in the budget terminals at airports. When I flew AirAsia from KL we left from the budget terminal. My flight was delayed for about 2 hours and there was no bathroom in the terminal. To make a long story short, if you fly AirAsia you'll inevitably become more low class after the flight. I'd pay extra to avoid AirAsia. It looks like you're saving money, but the flight will cost you for more than the eye can see.
It's fine though if you're on a budget.
It's fine though if you're on a budget.