From what I remember biggest difference is that Intel designs and produces chips. Where ARM only designs chips and everyone can build their own chips based on the design of course paying license fees. So Broadcom, Qualcomm and others are building ARM chips and would not be surprised if Samsung and Apple soon build their own.

Edit: Yes Samsung has something called Exynos, Cortex is from Broadcom, Qualcomm has Snapdragon. Basically there is much more competition in ARM.