You are posting in the wrong thread. No Samsung TV ships with Android TV OS.. It's either SmartHub or Tizen. Sony does equip some of its models with Android TV OS, depending on the firmware and hardware, it may be bad. Better to get a dedicated external player for such. There are dedicated thread for such external devices.. Can read all about em. If you still decide on getting a Samsung TV, then do so and buy an external device to hook up to it for added media playback (TV has usb and wireless media playback).

As for brand and model with decent "real" HDR, it's all about your budget. See few posts back for the popular model.

No idea on repair cost.. Most times whether flat or curved, the cot of repair outside warranty is so steep, might as well top up and get latest tech. Manufacturers have to make profits.. 

Spec wise is more or less identical. But whichever your budget tell you to.

Just take note that if you don't need the TV in a hurry, the MU series will be starting their price slash within this 4-5 months

In fact the price slash already started, but the amount will only grow bigger as time pass.

I thought MU6300 is the curved version of MU6100, are both different?
There is nothing exciting about the MU series this year from Samsung, picture quality is really average. Still hard to decide on the right 65" flat TV to buy for below RM10k.