I don't really get it, other than a different manufacturers take on the pistol market and their solutions to their customers opinions on pistols
My opinions on the advantages/disadvantages of the Tiberius and tpx designs have been on this forum a few times.
As a standalone single pistol the Tiberius is 'better' as the player can manage their magazines and 12 grams to ensure they are always ready to shoot at a decent velocity. To achieve this you have to commit 3 or more magazines with 12 grams and can fire off 3 loads of paintballs per 12 gram. Monitoring how many times you have used each magazine using the clicker on the bottom.
On a remote line the tpx becomes the winner enabling you to keep on swapping magazines
But it you mount an air cylinder to the pistol it becomes disbalanced. I tried to 'back mount' a 13ci cylinder but it just felt wrong to me and made the pistol too long
I used it in anger with the cylinder front mounted under the barrel. Still a bit too long but usable.
I had to lift, aim and fire. Anything longer and it would begin to tip my hand forward
A back mount as shown will tip backwards, but I never tried that configuration for real so don't know if the effect will be more or less due to the position
I've used pistols on a remote line many times, I'm not keen on it as I either feel the tiny drag of a coiled line or have the excess of a long line
My overall preference is twin pistols, which allows the pistol to remain basic as it was intended and I can play as I wish, managing the pistols seperatly so I run out of paint or co2 in one pistol at a time only, or ignoring practicality and running around firkng alternate shots from each of them like a demented idiot
With the milsig design I don't like the idea of a back mounted cylinder
The separate 'magazine' for a 12 gram looks like a workaround between the two methods of tpx/Tiberius
I don't know what benefit it has over the Tiberius magazine other than that you could carry 3 paintball magazines per 12 gram magazine.
If you can hit swap a part used 12 gram then you could manage you ability to be sure you have maximum shots ready, but I would think it also goes back to the Tiberius problem that you have punctured x number of 12 grams, whereas the tpx lets you load a 12 gram and not puncture it until you shoot
(I don't know if milsig have a similar puncture system)
Like @Cannon Fodder says, there are ways of doing fast 12 gram changes if you need to, and the Tiberius covered these
(As standard you needed to carry a hex key tool, which could be used quickly but could fit quick changers directly to each magazine, and in the very early days of paintball there were many quick change solutions for 12 gram shooters)
If the milsig pistol is anything like the other milsig markers, then it will be a pile of poo.( just my personal opinion)
I don't know anyone that's kept one for any length of time.
I've tried a few pistols over the years and the Tpx seems the best of the bunch.