Bryn,
I was using the Gamebore prior to switching to Armusa (a few months ago) and IMO they perform well. Certainly in the 20 gauge and 28 gauge skeet loads which are my main useage of Armusa. Enough to convince we i was going to use Armusa for the rest of 2014 and going forwards. Have dropped Gamebore totally apart from the few i have left.
I used the Armusa in my recent win at the BSSA UK Open (apart from .410) as did the runner-up!
I have pattern tested most of the Armusa range through my gun - the 28gram trap / sporting in 7.5's looks "tight" certainly at 40yds (60ft) which is my primary focus with me only shooting skeet which bodes well for longer distances on the fast trap and sporting shoots which are there primary use. However i have not patterned them at any longer distances although i will when i can find time to fit it in.
In terms of how they stack up directly against the Remington's - you will have to try as i only use Remington in .410 (and Gamebore for practice) and not shot the Armusa .410 yet as still have around 350 Remington left and approx 500 Gamebore.
Coincidently the Gamebore .410 is not even close to the quality of the Remington. So the Armusa .410 is going to need to be GOOD!
As a side note my wife is getting a flat of 250 of the 24gram Gold Serial to try for OT in a couple of weeks - will be interesting to see how they shoot. Given the same cartridges were used to win the recent Munich World Cup OT (Mens) and the recent Spanish UT Championships. Plus the price is RIGHT which counts for a lot!!