I've have a pistol-style Bosch IXO myself, and have used it quite a lot on occasions. It seems to work well for me.
Unfortunately, I've not tried a sonic-style screwdriver to compare them.
Having pondered it a little, I have a feeling that pistol-style might be slightly easier to use, as you don't need to tilt your wrist to hold it. And the button/trigger should wind up in a convenient position more often. But it might be quite a small difference, all in all.
As a tiebreaker, have you considered whether you liked pretending to be a cowboy or Doctor Who as a kid?