I have a GoPro 3+ black and a SJCAM 4000 that are both 3 years old and been flogged almost to death.
The 4000 is a great sacrificial camera where you don't want to risk a fortune with it getting clouted by rocks, trees or drowned etc.
Both have great video but the 4000 does suffer from sudden light adjustments more than the gopro. (but at a 100 bucks purchase price at the time it's outstanding.)
The stabilized SJ's are really good at steady video in a high vibration situation but they do crop the field of view to achieve this.
There is no way I would buy another GoPro when I can have 3 other cameras for the same price that achieve the very same quality.
SJ are right up there now as my mate has a SJCAM 9000 and it kills my Gopro with image quality in rough situations. (landsailing/kite buggying) My son has a Gopro 4 and it's over rated I reckon. Battery life is crap on the GoPro 4.
PS: I'm not chasing studio quality 4K video though. 99% of what is captured is ho hum throw it away footage anyway. I'm happy with 1080HD.