Ive owned both, Mk5 Golf Gti so much a better car for the Daily drive. comfertable, reasonably quick in standard form, easily tunable if you require more power. Turns heads as you do not see them all the time. MPG is reasonably good, my one filled with all the toys xenons, leather, tv/sat nav etc so does make it a nice place to be. after coming from a mk4 Gti Turbo, such a improvement over the mk4 especially in the handling department and appearance.
The cossie is nice, but for me would be more suited to the weekend toy.