I've driven an '03 or '04 GTI VR6 before. The styling was tight, clean, and buttoned down. The interior was surprisingly nice. But despite the V6 it seemed really wheezy. The shifter sucked on it, very vague, very tall, long throws and you didn't really get much of sense of what was happening down in the gear box.
I've not driven a newer GTI. Perhaps they are better?
I've not driving the Mazdaspeed3 but I"ve driven other Mazdas and based on those experiences I have a fair amount of confidence in Mazda's ability to build a fun car. And everything I've read regarding hot hatch shoot outs confirms this with the Speed3 coming out on top.
Then there's the specs, too. The Speed3 is lighter than the GTI, has more horsepower, significantly more torque, higher top speed (if that's important?), and a torsen LSD.
Although, one review was whining and complaining about the Mazdaspeed3. The problem: too much power.
VW GTI w/ 2.0L Turbo 4 cyl.
200 hp @ 5100 rpm
207 lb-ft @ 1800 rpm
3255 lb. (16.3 lb/hp power-to-weight ratio)
0-60 = 6.4 sec
1/4 m = 15.0 sec
Top speed = 130 mph
Mazdaspeed3 w/ 2.3L Turbo 4 cyl.
263 hp @ 5500 rpm
280 lb-ft @ 3000 rpm
3064 lb. (11.6 lb/hp lb/hp power-to-weight ratio)
0-60 = 6.1 sec
Top speed = 155 mph
Comes with torsen LSD