While delta E= 4 isn't a huge error unless it's in a low chroma color, it is still puzzling to find, but just because Adobe Color utility is consistent with the null transform trick (which also relies on Adobe components) on Mac 10.7 , doesn't necessarily mean Adobe has found the "pure" unaltered data path and Apple hasn't with Colorsync Utility. If one actually completes making a profile with these two approaches, then makes prints using printer manages color (as Apple presumably thinks most of it's customers do if they choose colorsync settings), and lastly performs a delta E test comparing predicted to actual output, the outcome could possibly tip in favor of the Colorsync utility accuracy. One reason I suggest this is that I never was able to get totally consistent target generation across Mac OS 1.5 on Power PC to 10.5 on Intel and 10.6 Snow Leopard (Intel only). Differences even larger than what Andrew has reported kept cropping up. That outcome leads me sadly to believe that nowadays custom ICC profiles may not only be printer/ink/media/driver-settings specific, they may be OS specific as well! Also, Adobe Color Utility totally failed to "hijack" the printer pipeline when I tried it in conjunction with my Canon ipF8300's "Free layout" printer driver, even though the appropriate settings were grayed out. So, like Onsight, I just use the Canon 16 bit plugin for target generation. That works great, but of course, only works for certain Canon iPF printers.