I like Altium Designer's ability to save a revision of my design in a
revision control system.
This is handy when trying to find an older version of the design, or
those occasional moments when I realize I screwed up and need to back
track to an earlier version (yeah, it happens).
Altium Designer also can show schematic differences graphically, graying
parts which haven't changed, and making very visible the parts which
have changed.
Why GIT? GIT works well when a network connection to my server isn't
available (on an airplane, bad connection, expensive connection, etc).
It also works well when there is more than one server involved in the
design (scales well).
I'd love to see this in Eagle!
--
Thanks,
Craig