Wow, someone my size/shape who's trying out the same saddles I'm looking to get! Let me know how the Galibier compares.
My Fizik (the old style, before they had the different versions) is a nice width for me, but I've heard leather saddles need to be a bit wider (so you're not sitting on the rear crescent piece). Have you had any trouble with the Aravis' width (chaffing/rubbing you thighs, etc)? How was the sit bone and perineum areas? These are my issues with most saddles. I'm typically in a fairly aggressive posture (not really racing, but not touring, either), but I'll sit up and grind it out up hills.
I've got my Fizik Arione mounted almost all the way forward on a Thomson setback seatpost. I did see that the rails are farther back on one saddle than the other, so I'll have to see which would have more room to mount forward on the seatpost.
If the two are about the same in comfort, I might go with the Aravis. It's heavier, but a little more versatile for mounting saddle bags (I rarely need anything more than spare tubes and a few tools, but it's nice to have the option when I do need to carry more).