I've always had D handles as long as I (and my Dad before me) had jigsaws - I'd never even seen a barrel grip in the flesh until a couple of years ago as they're not common in the UK.
Having said that, when I got a Carvex, I tried both and decided on the barrel grip. My mate has the D handle version, but I still prefer mine!
The only negative thing I can say about the barrel grip is it's considerably longer than the D due to the way the battery fits. It can sometimes restrict you when you're trying to cut in a very confined space.
Oh, and I now make almost ALL my cuts from below the workpiece now, which is something I'd never done before.