The Xbox 1 is purposely oversized

[sethnintendo]

Barozi said:

What does MS gain from constructing and selling a console that's purposely bigger than all the competitors?

Designed for Americans (you can remember us as the gas guzzler SUV/truck race).  Bigger is better is the usual saying (well at least in the state I know reside in, Texas).  They are just catering to their main consumers which is N.A. and U.K.