I happen to be running both ORIS and GMG at the same time. We are in the process of switching over to GMG.
Both systems work well and I have gotten great color matches out of both of them. You can easily create a "certified" proof with either system. We are switching because the GMG proofs have an almost indefinable "better" quality. They just look and feel like a slightly higher quality proof. I did a double blind test with our top 10 color guys comparing ORIS and GMG proofs on the exact same stock and from the exact same printer. GMG was preferred as "better" about 65% of the time, though there were some people who preferred the ORIS "look", possibly because they were more used to it.
One area where GMG beats ORIS is in fine resolution rendering. I don't know what resolution that ORIS rips it's files at because there is no user controllable setting. On GMG we were able to try several resolutions and at 720dpi it renders type and linework noticeably sharper than ORIS. That definitely contributes to the overall quality.
GMG is definitely easier to set-up if you are using their stock and are going to a known spec like GRACoL2006_coated1 or FOGRA39, because they include pre-built calibration and color transform files that work great. Just run the calibration routine and you're in business, making certified proofs. ORIS doesn't include any pre-built files, so he have to build every proofing queue from scratch. However, perhaps because I only have a few months experience with GMG, I have had a lot of difficulty building queues for 3rd party stocks for which there are no supplied files. Not only is the process pretty convoluted and non-intuitive, but I have yet to get it to work! Every time I create a calibration set-up (MX3), it produces a gamut that is too small to make a GRACoL proof. I've tried it on 2 stocks on an Epson 4800 and still no luck. I have been able to successfully build a GRACoL queue for both stocks on that printer using ORIS, so it's clearly not all bad! I admit the probability that I am doing something wrong when setting up the GMG queues, but still, a number of hours invested and still no success.
The advantage of canned files for GMG stocks is that you rarely have to create your own files. The disadvantage is that when you do have to make them, it's difficult. Because I have to start from scratch with ORIS every time, I am quite skilled on how to build a queue!
Overall I recommend GMG, but with either product there is a learning curve and it will take you a while to get comfortable with either system.
