Coal. I like the specs of the 6p and would happily spend the extra for it but I feel like a 5" phone is the perfect size so don't want anything larger.
The only issues I've had with my Nexus 5 are the odd random restart which bizarrely seems more frequent when not using the phone and it's simply sitting on the desk. Also, the compass on my phone always seemed to be off around 45 degrees when using maps or nav.
Any other issues to be aware of with the Nexus 5x? I rarely use the phone when it's charging other than as sat nav in the car. Presumably it won't affect that simply running if the screen isn't being used?
I have to say from my experience so far with the 5X it can be either a) a delight or b) a nightmare...now hear me out.
When everything ticks along nicely the 5X is a fantastic piece of hardware which has snappy performance with a great screen and feels great in the hand.
The camera is second to none and I do find the shots I've taken with it come out right...first time.
However performance while generally great can turn into stuttering mess at times which can be frustrating. This is more than likely down to the limited ram (2GB) however more than likely down to the combination of apps installed by whatever user...your own experience is going to be vastly effected by this factor. This can be solved by either clearing the cache...but a more solid fix is to restart your phone.
Also when things do get intensive for the 5X things get warm, then you notice problems and then you get pretty drastic battery drain. Most days I am easily getting through the full day but sometimes for unexplained reasons or I've decided to spend a bit more time using the device, in terms of a demanding app, I am reaching for the charger.
The good thing about the 5X however is it WILL get better with age, this was the case with the Nexus 5 and if you read around the web issues with performance have been discussed at length by many, this will no doubt be addressed.