I took a lot of pics trying to compare / contrast the GT vs the VX, as well as took a video of them both shooting to try and hear if there is a difference in the sound signature.
I will put comments above each photo as well as the video.
Here are both drivetrains. I'll go into the differences I observed on an individual basis in later photos.
The powertube and powertube cap have some differences. The front of the powertube on the GT is flat, where the VX's is more rounded off. The powertube mid o-ring is an 011 on the GT, and 10x1 on the VX, and slightly more forward on the GT. The powertube cap is different in size, but that difference only seems to be due to the fact that the attach to the guns differently.
The valve kegs are slightly different. The back section of the VX is a bit longer where it screws into the powertube cap. Also the VX's is closed off a bit on the back where the valve stops, where the GT's is wide open with a lip inside to stop the valve. You can't really see the lip inside the GT's valve keg in the photos, but it's just a small lip.
The valve on the GT is machined to accept the larger 017 o-rings as opposed to the (2) 17x1 and (1) 15x1 on the VX. Other than that they look pretty similar other than the back of the GT's valve being a bit more rounded off.
The bolt kegs in both the GT and the VX are identical. The spacer is identical too.
The only thing I can see different on the bolts would be the obvious thing...the venturi style cap on the GT bolt. The cap makes the GT bolt a tiny bit longer...perhaps in addition to the cap, the slight length increase assists with making it handle brittle paint better due to there being slighly less of a gap between the ball and the bolt when the ball enters the breach (I'm totally guessing here). I really don't see why the red bolt couldn't be installed in a VX (I take no responsibility if you do this and something goes wrong).
I figured I would include the Militia Lube in this comparison. I don't know if there were intended differences, but the lube I got with the GT is quite a bit different in terms of thickness. The VX's is the browner color, and the GT's is the white. When I ordered the VX I got a 2oz tub of lube as well as what came with the gun, and it also was the brownish colored lube.