Squall's gunblade is made to be used two-handed, as can be seen from the design of the handle. The handle's also not at too steep an angle to the blade, so it'd be less difficult to swing. Seifer's Hyperion, however, would be a real challenge, since it's clearly a one-handed design. The handle's almost at a right-angle to the blade... that's probably why Seifer always takes those 'roundhouse' swings with his weapon, and why he braces his free hand against the back of the blade when he parries - it's the only effective way to use it. Try holding a golf club by the head - an old one, not a light new graphite one - and you'll have some idea of what the Hyperion's like. It's only advantage over the revolver is that the gun aspect would be easier to use - bigger capacity, simpler action, better 'swing' for taking a shot.

Edit: Your new sig is freakin' hilarious, by the way.:bgl: