What are your tone requirements? Those two cabs probably sound very different from each other. (Paging Bstring!)
Those two cabs come from two different angles as far as disign. The Ampeg 8-10 (or most of them anyway) are sealed cabs. What they really are is 4 separate air tight 2-10 cabs in one big box. They are low mid walls of sound! But don't go trying to get earth shaking ultra low frequencies out of them. They are built for it. They are great for that vintage low-mid good old rock and roll punch.
the GK is a modern cab. It's ported and had horns (tweeters). I'll bet that thing can throw some low frequency air like most cabs can't. Not to say that you can't dial in some great mids.
The point is their out-of-the-box tones are probably worlds apart, though both have their strong points.
If you're gonna be stupid, you gotta be tough. - My Grandmother