So, let me begin with what started it all: the first film, Ghost Busters. These comparisons will focus mostly on the pack and its construction. There are 2 variations of proton packs used in the film. The Hero and the stunt.
The GB1 Heros
The GB1 Hero proton packs were fiberglass shells mounted on aluminum motherboards with LC-1 ALICE Frames and straps. These packs had many aluminum parts on them, including: aluminum Ion Arm and cap, booster tube, injector tubes, HGA, vacuum line, PPD, Beamline and filler tube, as well as the N-Filter. The wands for these packs were also fully aluminum, minus the resin grips. All these external parts were pop riveted to the shell, which was then, in turn, mounted to the motherboard via L-Brackets and bolts at the 4 corners of the pack.
Here is a close up of an aluminum Hero wand.
The GB1 Stunts
The GB1 Stunt packs were packs that were cast in foam to be worn during physical stunts performed in the film. Many of the attached pieces of the hero packs are cast on to these packs in foam. These packs also featured static lights and were attached to plywood motherboards with different straps compared to the GB1 heros. Other then the bumper, wand and hosing/ribbon cable, everything was cast into the foam shell of the pack.
In this photo, I have several parts of the pack circled and numbered. Number 1 is a toggle switch for the lights on the pack. Numbers 2-8 are all parts that on the hero were metal and mechanically attached to the fiberglass shell in some way. On the stunts, they are all cast in, and many have been filled in around them with material to remove undercuts from the mold. The most obvious ones you can see in this photo are for number 4, where both the filler tube and beam line have material attaching them to the EDA. Another way you will notice the stunt packs is that the Ion Arm (number 5 here) is also molded on backwards in relation to the hero packs.
In this image, you can see the the extra material underneath the injector tubes here.
In this image, you can see the extra material under the HGA to eliminate the undercut under the molded on HGA.
That's it for the 2 different packs from Ghost Busters.
Next we'll move onto Ghostbusters 2: Electric Boogaloo.