Actually eServ service is not as good as QCD. As far as I bring most of my customer Mac to service and a regular customer on eServ and QCD, QCD is because QCD office is not look as class, and the location is not as like orchard road, therefore feeling the service might not as good.
Example I went to eServ to customer MBP hdd cable is not working, and hdd is about to died. eServ change for part cost over $1800++, while the QCD engineer called me and said I have the pay the HDD cable and the HDD, they will waive the service charge and install the OSX for it. Total cost is 850 + GST. way cheaper then outside.