The Magnuson-Moss Warranty Act prevents dealers from voiding your warranty just for using a third-party cold air intake. They would have to prove it caused damage to the vehicle.
It's not easy to get a unbiased opinion on anything online. Most people can only afford one brand, they aren't trying them out and comparing numbers. I think the Banks has the SXTH beat for airflow and engineering. Some people like the way the SXTH looks; personally I think it looks a little...