I've got both - bought the System 5 for practicality and the Tour-X for cool looks.
Depends what you're doing and what your bike/screen setup is. I ride a Dakar with a big-ish screen.
At slow speeds (eg in town and off road) the Tour-X is great - well ventilated, looks great (esp with tinted visor) and keeps the sun out of your eyes. Visibility is excellent with the hugh visor giving 180 vision.
At anything over 50-60, however, it is a completely different story. The constant droning of the peak together with the instability caused (I think) by the huge chin piece; the openness of the chin piece (which causes a huge draft over the face/eyes which is great in hot weather but a pain for a long journey/cold weather) and the general noise make this a complete no-no in my book for long journeys - I say this having just come back from 4500 miles in Norway wearing one!
System 5 doesn't look as mean, but for long journeys at speed (as much as my Dakar can manage anyway!) it is absolutely miles ahead of the Tour-X - more comfortable, quieter, better visor (easier to swap over too as no tools required unlike the Tour-X) less drafty in cold weather and with flip up.
I'm lucky to have both, but if I was to only have one it would be System 5 - no hesitation. (With maybe a £50 moto helmet for muddy adventures!)
Everyone's different tho - only my tuppence worth!
