How is this an improvement over the factory ACR piston setup?

Advance warning:  I don't own Marvin's ACR gas system yet.

Advantages I'm aware of:
Lighter
Can extract piston from front of rifle without removing anything else
Fine tuneable
AVAILABLE

Read this thread for greater detail:

link to Nefarious Arms gas system review

The piston comes out with the regulator just like with the factory system.  

Here's a pros and cons

Pros

Lighter

Allows the use of a factory AR gas port.  Normally you would have to plug it and resize since the ACR uses gas more efficiently than an AR.

Available, although not sure if he'll sell it without a barrel

It's not nessarily more tunable than the factory system but you can send just the regulator to be tuned where as the barrel has to be sent in for the factory system

The guide block allows the use of more barrels

It's pretty


Cons

It's very very dirty while the factory system is down right spotless.  If you hold the handguard over the regulator you'll end up with black hands.

It uses gas rings which are a wear part that was purposely designed out of the ACR to make it as long lasting and bullet proof as possible.

The piston assembly can move out of the regulator when over gassed resulting in the rings being melted and wrecked.

It is actually more difficult to switch settings, especially with the handguard still attached.  The factory regulator only has one position that removes it so when you go between settings it stays put.  This one pops out pretty aggressively. Not so much an issue when it's not covered.  

If Marvin will not sell separately, you're looking at a bit of a wait.




Personally I prefer the factor system because it's very clean, very simple and very rugged.  If the world ends the ACR in its factory condition will put last you and any other rifle.  Nothing wears, nothing really breaks.  

But since his is actually available, if it's available, I would love a few more of his.  The fact that you can just pop it on a barrel and not really touch the barrel is a huge plus.  Ordering another regulator is much easier that having your barrels gas port resized.

Thanks for the extensive write up, right now I'm just trying to save for either his or Danas conversion. How is margins piston system attached to the barrel  as you mentioned you could just swap it between barrels easily.