The guillotine puts on a better show. If the blade descends with enough speed, the head leaves the body with a great arc. You could put a basket nearby to catch the head and yell, “Two points!” when it hits. The tremendous flow of blood is entertaining, too.
A guillotine is too quick. Hanging is much better, especially if done by miscalculating the distance needed to drop the perp. You want these guys to have to do a jig for about 20 minutes while they are slowly strangled. You get to watch them pee and/or crap their pants, perhaps have their eyes bulge out, and their tongue hang out of their mouths. Great fun for all.
Or, you could hang, draw, and quarter them, which is a lengthy process as well.
Just so messy! And the sharpening and all.
Besides, I'm rather something of a cowboy, you see.