The IQ of the old lower resolution GoPro Hero actually compares favourably to the Action 2.  Problem with the Action 2 is saltwater.  The contacts can microscopically corrode - rendering your card completely unrecognized in-camera.  The card is in - but is not visible to read or even format.  Fortunately was able to clean the contacts perfectly and all is good again.  So take away is to not use the Action 2 in saltwater without an airtight case.  In another thread I linked a post where saltwater caused major corrosion.

Comparatively the old Hero actually uses an in-built non-removable underwater case.  This is definitely a safer option as it is completely airtight enclosed.  While the footage is not stabilized and not 4K - it was acceptable for a quick action cam capture.  Moving forward will continue using the Action 2 for freshwater shots - but underwater salt will use the enclosed Hero.  The Action 2 contacts are a little bit too sensitive to saltwater - risking losing use of the card and external storage completely.  The contacts allow the external storage to read and function properly.

Even though the internal storage had the files - the contacts restricted transferring to the card that was not readable.  Device could charge - but card was not even visible.  Possibly you can pull the files via cable - but the major concern was no access to any card inserted.  As noted problem was solved.  But is a PSA for any Action 2 owners planning to use in saltwater without an airtight case.  As someone posted elsewhere - the waterproof cases for the Action 2 are not always 100% waterproof.

One screenshot of the Action 2.  One screenshot of the old unused 2015 Hero.  Hmmm?  Nice.

Thanks for that info and comparison. Found your post after your kind reply to my thread about the Action2.