Well some attributes for each:
For tunes both PHP and Edge have good tunes but PHP's are a little bit better because they dont have to follow CARB guidelines like Edge.
Data logging-May not seem like a usefull tool but if you want to check how some things are running more time is better than more parameters IMO.
The Edge can record 6 parameters for up to 1 minute
The Gryphon can record 5 parameters for up to 6 minutes
The gryphon can be upgraded if for some reason you do make some kind of modification or would like a custom tune designed for a specific goal like heavy towing or better economy/performance.
You can also change the splash screen (opening screen) with the gryphon to show whatever you like.
Here is a link to that section of the forum:
Splash Screens - Power Hungry Performance Forum
And like shotgun said, you can paint it if it doesn't match.
Other than that they are pretty much the same. The gryphon just leaves more options for customization.