1070 or 1080 in a laptop: What's better for low heat?

[Dreepa]

So when it is all about heat, and that shall be the only deciding factor, is it recommended to go with a 1070 or a under-clocked 1080?

Can a 1080, when throttling it become more heat efficient than a 1070?

 

[rgd1101]

MERGED QUESTION
Question from Dreepa : "1070 or 1080 in a laptop, when HEAT is primary concern"

So I was wondering:
If the No.1 prio is getting lower heat, is it better to get a 1070 or 1080 and throttle it a bit?
Is a throttled 1080 producing less heat than a standard 1070?

I would like to get an Alienware 17 (no max-q).