The Graphite Comp and the Graphite Pro are different critters from the Graphite, but all three are great sticks. I don't have a GPro to measure, but I remember it being the same size as the Comp – which is ~103 sq in versus the Graphite's 107. ("Series 110" was just the marketing department's way of saying "oversize".) That's the biggest difference to me, but I have always been more sensitive to head size than to most other specs.
As pointed out, the Graphite is noticeably stiffer than the other two. Stiffness variation in those days was largely accomplished by varying the ratio of carbon to softer fibers, and if memory serves it was Graphite (100% carbon) > Comp (80% carbon / 20% fiberglass) > Graphite Pro (60% carbon / 40% fiberglass).
Note that there are two versions of the Graphite Comp: the first had individual grommets and no bumper guard; the second grommet strips and bumper guard. If it reads "Comp" (not "Graphite Comp"), I believe it is always the first. If it reads "Graphite Comp Series 110" I believe it is always the second. I also believe there are some that read "Graphite Comp" without the "Series 110" that can be either version. I played in college with the first version and loved it. I have a couple of the second version now, for old times' sake, and I love those too.
If you decide to chase down a Comp, it won't be difficult or expensive. (Try to get one with that gorgeous green (faux?) suede cover in good shape, if you can.) I don't see as many Graphite Pros around, but there are some, and they are cheap too.