^ Agree ^
The only reason I switched (2 reasons actually) to S5II's was:
A. I needed more reliable forward motion AF tracking. The AF of the first gen FF S line cameras was and is perfectly fine, except in this regard when it can be a bit hit and miss and just one miss with a critical unrepeatable scene and it's gone.
I shoot weddings so I am thinking bride entrance, confetti walk etc.
It happened. Several times.
B. I shoot outdoors mainly and some days, over 35c / 100f, direct sunlight and without a fan is not good.
I never had an overheating issue, but it could just have been a matter of time and was constantly on my mind.
With the S5II's, they still get hot, but I am not concerned.
_
I have personally never noticed any file quality difference between the S5 and S5II, but then never shot them side by side and 6 months apart.
There may be a difference, but nothing I have noticed or concerns me especially.
IMO, the S5 is the budget filmmakers bargain of this current decade.