The A72 is supposed to be as fast as a Core M Broadwell core at 2.5 ghz( assuming that the A72 maintains clockspeed while the Core M throttles, which is the case in most fanless laptops). The rk3399 is clocked at 2.0 ghz on the A72 cluster so it's slower but it has the benefit of the neon SIMD extension set for future codecs( should someone want to make it work) and dedicated ip blocks for a lot of stuff.