I had one years ago, a mossberg 500 with the pistol grip butt stock and a pistol grip on the forward as well. It had a heatshield, extended magazine, folding stock, all the bells and whistles. It looked awesome hanging over the bed, but even after doing all that work putting on the "tacti-cool" stuff, I never shot it. My little brother practically begged me every time we went to the range to bring it, but I never did.
He borrowed it from my wife one weekend while I was out of town. All I remember was getting a phone call saying lil brother had broke his index and middle finger while shooting that gun. He doesn't even know what happened, but the gun was at a pawnshop the next day. I traded even for a gorgous mossy 590. That pump always gave me a weird feeling, it had bad juju in it, and I have never thought about another.
If your dead set on pistol grip, the market is pretty cornered by mossberg and remington. I do remember seeing a Stevens new model that's all decked out, but the model slips me. And I know a local shop here has a Rock Island pistol grip. It's cool if not for any reason other than the jeweled bolt.
Follow Dave's advice and borrow a buddies. And as dascottsman said, to each his own, & as with any tool, practice with it to learn your strength and weaknesses. But by all means, borrow one first. See if you like it, that way your not tossing hard earned cash at unicorn you are chasing just to catch it and learn its a shetland pony...
I don't know about jmr40's experience with mossbergs safety, but I have mounted
these on friends and families guns and they have worked fine for them.
Goodluck!