I have used both. IMO, the Metra Axxess is the best of the two. The PAC was extremely slow, the wiring was very thin and it was a major pain in the butt to get working.
The Metra has worked flawlessly for over a year. I think it's easier to program if there is manual programming needed. It has an automatic feature, but sometimes doesn't work with newer units. Even if it doesn't work, it's not a big deal. Only took me 10-15 minutes to set it up manually and most of that time was me reading the instructions.