GoPro cameras continue to add features and enhancements. If you consider cost and the added features, you will find justifications to support purchasing any of the different versions available.
- The Hero4 silver was the first to incorporate a built in display.
- The Hero5 introduced image stabilization, higher frame rates than previous versions and offers other features that while not as functional for divers, they are pretty significant such as GPS, voice commands, improved sound recording quality and waterproof for snorkeling.
- The Hero6, for $100US over the Hero5, introduces higher frame rates, new processor and enhanced image stabilization.
Any one of these versions of GoPro cameras offer a good bang for the buck. I don't recall what I paid for the Hero5, but I can't say I got a bad product nor that I have any regrets form getting it. That goes for the 2, 3+, 4black cameras. These are all pretty good products and still work well.
The take home message here is that I don't think you will go wrong getting the Hero6. If price is an issue, then go with the Hero5. Still too much money, the 4Black and even the 3 series will deliver good images.
Cheers,
Ricardo