Sony also seems to be smaller than Xbone:
XB1: 34.3 x 26.3 x 8 => 7,200 cm3
PS4: 30.5 x 27.5 x 5.3 => 4,400 cm3
So PS4 is 63% smaller than Xbone.
AND its power supply is intenral, while Microsoft opted for external brick.
But how come eh? Probably because Sony is (still, sigh) a hardware company and not a monopolist with oversized marketing department...
Now expect shit storms of FUD by Micro$oft "to compensate".