I had to make a decision so I am going to return my ZF8 to the store. I use WhatsApp videocall on a daily bases and it makes the phone really hot and drains the battery. Too bad, because I really liked this phone... Example of today... 1,5 hours of gaming just took 3% and 30mins of videochat took 50% battery.
Looking up the heating issue it seems to be a kinda open issue with the samsung produced 888 chip and the smaller size most likely is not helping it dissipate that heat. But I do also see people reporting good sot time so I guess some optimization to the kernal might help.