Which one would you recommend for the 47? I see there are two different versions... Thanks

Look at your current gas tube, go for the M1-B if it doesn't have vent holes in it. Go for the M2-B if it does have vent holes in the sides, assuming yours is a standard AKM and not the Yugo type as those are longer versions.

It really doesn't matter. The holes don't make a difference in the function of the rifle.

AE knows. It don't matter 2 chits one way or another..

its a wasr...

Apparently, Kalashnikov thought it mattered.  As did FNH.  But what do they know?

I think the point is...if you have a vented gas block it still doesn't matter if you use a vented gas tube.  If you have a Chinese AK...of course use the vented one.

Then please school us, and I mean that sincerely. You know your shit and I would be very interested to hear your opinion on this. When K-Var had AK-105 combo blocks available I bought one along with their railed S-12 combo block and neither of them have holes on them. Now this could just be an anomaly, but it would seem that they now deem them unnecessary.

And I want to clarify, that when I said that the holes don't effect function I was referring to being able to cycle the weapon. The prevailing opinion is that more holes in the gas tube/gas block (in the traditional place) equates to less gas cycling the weapon, which is false. I'm sure the holes serve/served some other function.

I understand the function of the holes is to vent gas in a case of too much  pressure - such as bad ammo, or partial obstruction.  They are present on all AK variants, as well as the FN FAL.  

In normal operation, the gas necessary to cycle the action has already done it's job before the piston head leaves the gas chamber. Combock does not even call it a gas tube, they call it a "piston guide."  So from the perspective of the gun firing, the piston guide isn't even necessary.  It is for the piston to find its happy spot in the gas chamber.

One of the modernizations of the AKM over the AK, was to relocate these vents from the piston guide (gas tube) to the back of the gas chamber.  

So, as mentioned before, if you have an AKM, it doesn't matter.  Using the rail with ports in the tube is redundant, but not harmful.  But using the non-ported tube on an AK, means there is no relief valve. The AK will run just fine without the holes in either the piston guide or the gas chamber.  Unless you have an over-pressure situation.   What will happen without them, then?  I don't know.  But MK put it there and nobody has seen fit to eliminate the feature in 60 years of production.

I speculate that an additional purpose may be for operating when wet.  The Brits modified their L1A1 return spring tubes by drilling a vent hole in them,  and discarded the rubber gasket sealing the tube.  They  found that water or oil in the tube could create enough hydraulic pressure on firing to rupture the tube and blow up the stock.  While I am taking a design feature from one gun and using it to speculate on the purpose of a  similar feature in different application, in a different gun, I think my reasoning is sound.

In the 20 years I've been working on AKs, I've learned that there is not a single machine cut on the rifle that doesn't have a purpose. It is a mistake to assume that, because one does not understand the purpose of something, that there is no purpose.   For example, I used to think that the loose piston was sloppy 3rd world manufacture.  Until I translated the specs that identified the amount of wiggle that was designed in, and acquired the original gauges for measuring it.

Just get the M1-B then, I've bought 2 from AimSurplus and they were $88 shipped each BTW.