The reason for the GEN2 actually has to do with simplifying manufacturing rather than any change in how the regulator functions or performs.
As we continue to introduce more air systems, the more parts which are unique to each system and are not shared by other systems, the longer it takes to produce them since we have to break down and set up our machines to run each unique part.
In order to streamline production we have redesigned the body of the Micro Reg so that it can now accept the same piston as used the UGS and CGS since this was actually the only internal part which was different between those three systems.
By shifting the location of the gauge and output to the top of the regulator we no longer need the through hole on the Micro Reg's piston stem so it can use the same piston as the UGS and CGS which is also simpler to make. As an added bonus, we no longer need that center o-ring which drops the total o-rings in the system to just two. That center o-ring was a bit tricky to install so this also aids in speeding up assembly and makes it easier to maintain.
The two pistons are actually identical otherwise so as far as how the regulator functions, nothing has changed. It still produces 40psi or less on the low end of the pressure adjustment range and at least 130psi on the high end of the range. By having reduced drag on the piston from removing that center o-ring it technically is just a hair more responsive but this isn't anything you are really going to notice.
As far as the externals, the body has changed a bit in appearance but it is still just as compact as the original. The overall height of the body is within 0.006 of an inch of the GEN1 and the gauge sits a little higher but the overall footprint is basically the same.
Compatibility: Standard HPA, LP, and SLP air tanks
Material: Aluminum Alloy
Note: The output pressure of the regulator can vary slightly depending on the output pressure of the tank it is used with.