Only the opposite of what you're assuming. I test drove both, and obviously my GTI was the better choice- by far IMO. I drove my buddies GTI and I fell in love with the torques the VW made in comparison to the Cooper S.
Aside from VW engineering, the GTI was a much better bargain for my needs/wants in comparison to the Cooper S. I opted for the 337 model because it came with the stronger 1.8T motor, big brakes, 6spd and full Recaro interior. The Cooper S I test drove wasn't nearly as quick as my car, but did handle on a completely different level... if comparing stock Cooper S to stock 377. However, adding coilovers and a rear swaybar to my car puts it very close to the capabilities of the Cooper S, and still at a marginal cost.
It's all up to preference is what it really boils down to.. I'm happy with my choice, and i'm not trying convince anyone either way, the Cooper is an outstanding car.. just not my cup of tea.