:I have a 9m Berrata, but I don't have a holster for it yet.
I watched the movie predator and both styles are featured in the movie.
So which should I get; Harness shoulder type or an assault type that fastens to my belt and hip?

Where and when are you going to wear the gun?
The shoulder holster is great for driving and for concealment, as long as your jacket is on.
I've got the Galco nylon one with the mag pouches and handcuff case for my Berettas from years ago (can't remember the model name now) and it's my favorite.  I don't always wear that holster, but, it's my favorite.  
The Tactical rigs would be nice for a plinking day, but would probably scare people everywhere except Kennesaw, GA.

It seems to me that the Shoulder Holster is easier to hide. But, the belt holster would be better should you need your gun quickly. A friend of mine has a small half-holster device that hooks on his belt. This allows easy access, and with his compact pistol isn't readily visible. All it is, is a loop with a snap to secure the gun. A 9mm Beretta, M92 I assume, is a rather large gun and wouldn't conceal easily. Perhaps a Beretta M92 in a Shoulder Holster and an AMT Backup or similar Compact Pistol on your belt. the compact pistol would provide quick access if you need it right then. The Beretta would take a little longer to access, but would provide alot more firepower.