What would be the best sports action camera? what are the choices that you have? You can buy some of those cheap HD camera of an unknown brand made in China but you may face some problems in a few months later. If the product shows defects within the same month you purchased them then you may be able to claim your full refund from the supplier. The problem is, the defects starts showing up after a couple of months where you may be no longer interested to use the product as frequent as when u newly purchased them. At this point of time you would not really mind to claim for warranty as it may cost you time and money. Would you like to send for repairs if it takes more than a month or up to 3 months? The product however most products do not provide warranty on the battery and a few parts even if it is very vulnerable. This is where the advantage is when you purchase a cheap products especially the one with unknown brands.
So I would suggest that you go for a good well known brand with great reviews to go with. This page will show you some comparison on available sports action camera and will primarily focus on GoPro products.