They are radically different guns, especially in 12.
The Citori is heavier and much taller. Put a 30" barrel on it (or better yet a Superposed, which balances the same) and I love it. Put a 26" barrel on it, and I hate it. Seems like it wants to go up and down but not side-to-side, because of the weight distribution, with a short barrel.
The 686 is a low-profile gun, more side-to-side but a bit less tendency to move vertically than the boxier Citori when you swing it. (Browning's Cynergy is similar)
So it's not just about fit, it's about your body weight distribution, your shooting style, what you want to shoot at, and what length barrels you're looking at. Since the gun is an extension of your body, it all depends on how well it fits YOU, and not just the length, either.
Do you mean sporting clays, trap, or skeet?
A 30" Citori is a wonderful trap and SC gun, but I wouldn't want it for close-in doves, for example.
If you can, try them both. At least swing them both a lot. Try different lengths if you can. Close your eyes. Feel what you like. Open your eyes, see what you like.
They're both excellent shotguns. They just feel so different, that's how I'd choose.
(I just returned a Superposed I'd been borrowing. I want it.
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