You don’t know if Intel’s x299 is better than the x399, none of us know. Going by history the x299+CPU’s should be good and AMD has a tenancy to shoot itself in foot, repeatedly. I’m hoping they don’t this time. If nothing else they have pushed Intel off their fat over paid butts.
I think it's safe to say how it will pan out.
for the same price, you can get more cores from amd, or you can get slightly less but faster cores from intel.
or, if you need literially the very best money can buy, you can churn out 2k for the 18 core, which does seem like plenty of people will as the 6950x at £1700 still sold well