Heating issues are caused by background apps running at the same time. Most are seriously unnecessary to make the phone up and running. Powermanager in Marshmallow is kind of basic and the real solution is to have a systemless root and debloat all those resource hogs.
I was on Lollipop since June. I had mixed feelings about doing the upgrade because of the negative feedbacks some were experiencing. About 2 weeks ago, had the courage to go for the update. Voila! I ain’t going back to Lollipop.
Others prefer to stay with Marshmallow S_208 because of volte support. Pesonal preferrence really.
Flashing a full stock Marshmallow S_218 ROW will give the enduser less headaches against doing those incremental OTA updates.