They're all good knives. To me, the main differences are the grip, the point, serrations, and blade angle, and your preferences for each.
The Neil Roberts, the Pacific, and the Professional Soldier have a more comfortable (to me) thumb forward grip, while the Green Berets have a straight up and down hilt. Bill Harsey's designs have evolved for the better in that regard. I think the Pacific has handle scales more even with the edge of the tang, while the Green Berets and Neil Roberts have their scales slightly recessed from the tang to provide another grip edge (Chris Reeve's idea), possibly beneficial when wearing gloves. I don't own a Pacific (yet), so check with Heather on that, before trusting my memory.
All of them are basically variations of a spear point, except the Pacific, which is a clip point, with a slight swedge. They are all very strong tips.
The Neil Roberts and the PS are plain edges, while the Green Berets and the Pacific have serrations at the base. I think the Pacific is basically the Green Beret with a clip point and the thumb forward hilt/grip of the Neil Roberts, at the request of the 1st Special forces group. The Pacific also has the finger cutout in front of the hilt, so maybe it's really a Neil Roberts with clip point straight blade with serrations.
There's a maniac or two that has managed to break a Green Beret and a Project II(?) by beating on them with a sledgehammer. Yes, all tool steels are notch sensitive, and serrations are angled notches, but NOBODY has ever reported breaking any Chris Reeve knife with normal batoning. If you want to try batoning with a sledgehammer, use a non-serrated knife blade. I don't try to pry doors open with my knives, either. If I had to pry doors, I think I would buy a 21" Vaughan XL Superbar at Home Depot for $15 instead. Disclaimer: I don't work for Home Depot, I'm not a SF operator, and I don't pry doors open. I'd be curious to hear from from someone who is, and has had to, though.
The Neil Roberts has a slight drop angle to the blade, relative to the grip angle, while the others are in line.
I prefer plain edge, thumb forward grip, so I carry the Neil Roberts and PS more, but if you need to cut a lot of rope, the Pacific or Green Beret might be handier. If you grip knives with your thumb touching your index finger, the upright hilt on the Green Beret won't bother you at all. I do like the looks of its spear point tip more than the extended swedge on the Neil Roberts.
Or you could just decide to eventually get one of each, starting with the classic Mark VI before they quit making them this year. I guess I'm not the best person to call for Knifebuyers Anonymous. Hope you don't mine the design ramble.