This discussion on Hacker News has quite a few interesting points about the competing instruction sets and the costs and benefits.
https://news.ycombinator.com/item?id=12300373Also links within to the operation and economics of chip fabrication.
(The headline is about Intel moving to fabricate some ARM products - presumably because they have lots of capacity and can eke more profit out of having ARM being part of their portfolio: "this announcement is about licensing ARM's physical IP to enable the Intel foundries to fab ARM SoCs for other companies, not about Intel building its own ARM SoCs")