wew, damn it looks good !
let us know once u tried it out diving deep 

btw, ur official housing cracked? such mistakes by xiaoyi. can complain them leh 
before answering ur question.

FYI
hero3 black upgrade to 1st version xiaoyi = not an upgrade. 
xiaoyi 1st gen is actually almost similar in term of specification n quality compared to hero3.
xiaoyi 1st gen have their own discussion thread, u can have more info there -->  https://forum.lowyat.net/topic/3540306

this current discussion thread is about 2nd gen xiaoyi (yi4k).

psps. i misunderstood ur statement . 

my simple answer, i have yi 1st gen n yi4k
1. low light - video and picture captured is definitely clearer and less smudgy. more details.
2. bright light - have no problem capturing photo and video when facing bright light, the camera will adjust the sensor itself when changing from low <-> bright light, it may take <1sec like that.

its definitely a good upgrade from yi 1st gen and hero3. to yi4k
but not a must. unless u really wan the screen, OIS, 4k recording.