As with the GoPro Hero3 Black Edition, the Hero3+ Black Edition has the best video quality we've seen in the category as well as improved battery life, faster Wi-Fi performance, and a lighter, smaller housing. Also, if you want a lot of accessory and mounting options, a GoPro is certainly your best bet. All of that said, it's far from the only game in town.
The smallest Wi-Fi-enabled action cam we've seen, the Ego measures 1.3 inches wide by 1.5 inches deep by 2.5 inches high and weighs just 2.4 ounces. A quarter-inch tripod mount gives you a lot of options when it comes to attaching it to your gear, but Liquid Imaging also makes mounts specifically for the Ego as well as an underwater housing that's good down to 130 feet.
It might not produce the best video, but the whole MHD package is a very good value. It definitely makes it affordable to do a multicamera setup, and it's just inexpensive enough to make you want to impulse-buy one to play around with in and out of the water.
If you're looking for an action cam that you can take out of the box, pop a memory card into, and start shooting with -- even in the water -- the Drift HD Ghost is certainly worth considering. Its video quality is very good, but it's the whole package that makes the HD Ghost a top choice. Drift recently announced a follow-up camera, the Ghost-S, which adds new Wi-Fi features as well as better battery life, faster frame rate options, and a high-bit-rate setting for lower video compression.
DXG is known for big specs and low prices and that's what you get with the IronX. Its video is nothing special, but if you are most concerned with enjoying and sharing videos online and viewing on mobile devices, you get a lot for your money here.