Ok Grmblz
The little holes are all about back pressure. When we use a mixed gas, we still want the same amount of dissolved CO2 in the beer. Say we used 60/40 (always expressed N2 first then CO2) and we wanted in for instance a stout 4g/l of dissolved CO2 at 5oC, we would need 50kPa to reach equilibrium. The gas is only 40% CO2 so we need
50/0.4=125kPa, that would be a very low carbed stout. For something like Harp you need around 250kPa. Problem then is when you open the tap, the beer tends to do a U-turn in the bottom of the glass and hit you in the eye. Hence the flow control plate. Easy enough to look up the
solubility of N2 and CO2, believe me it doesn't take much coaxing to get it down to equilibrium. Turns out its N2 0.019g/L and CO2 1.69g/L (at 0oC and zero gauge) CO2 is nearly 90 times more soluable.
Trumsn
Haven't had either of those beers, considering the very real upper limits on the containers pressure ratings, I would be surprised if they got anything like the performance we get from widget packaging, have a read of the "widget" link above for why.
Mark