I am a member on the touran forums as I joined when I owned one earlier in the year. I guess it may be down to brake fluid issues, but if you look at the link more than 50% of the people on the forum have had the problem.
Hmmmm . . . . maybe there are some subtle differences - not between the actual hardware, but more to do with the 'ownership'. The Touran is obviously a 'family car', made to carry the little darlings to playschool and gymkhana - so will not 'use' the brakes hard or harshly. Whereas the GTI is a hot hatch, and many GTIs will get driven accordingly. So with those two points - maybe the GTI owner is more demanding on ensuring that it gets serviced properly (and wants the brake fluid change carried out), whereas the Touran owner might think that their brakes are far less 'stressed', and the BFC isn't really needed.
And another point on the same 'ownership' issue. GTI owners will have undoubtedly got their ABS and traction control to 'kick in', probably on a reasonably regular basis. Whereas the Touran owner will have probably never activated the ABS, nor the TC. So the Touran will have 'stale' brake fluid in the ESP modulators, whereas the GTI will have constantly 'purged' the fluid through the said ESP unit.
So perhaps you would like to inform the Touran owners:
- (a) don't skimp on the two-yearly brake fluid change - £50 every two years to save £1500 on a shagged ESP unit

- (b) get them to regularly 'activate' the ABS and/or traction control - to 'flush' the ESP unit
I was thinking about an 04 leon, but would prefer another Golf tbh.
Golf any day! Just make sure you change the brake fluid regularly.