But while both men were disappointed to start their latest European adventure with a loss, the tight nature of group's 1 and 3 mean the pair remain confident that leaving England and Wales with a point could ultimately prove invaluable.
"The nature of this pool, and the class of those in it, means that any point won away from home is very important," said McGahan after a late Sam Tuitupou try stopped the 2006 and 2008 Heineken Cup winners from departing Reading empty handed.
"Overall, we are disappointed with our first-half display, too many mistakes, too many penalties conceded. London Irish played smart rugby and deserved their win.
"People must remember that this is very nearly Test match rugby, so every error tends to be punished.
"But ultimately, we were denied by two great pieces of defence by Irish when we were virtually over their line. Those hits were crucial to the outcome because they came when we were pushing them backwards yard by yard."
As for Edinburgh, Moffat admitted falling just a point short in the Welsh capital was hard to take.
But at the same time, the affable Scotsman was under no illusions that the result could have been worse had the normally reliable Dan Parks had his kicking boots on.
And with no clear favourite to take top spot in a pool that also includes Northampton and Castres Olympique, Moffat knows that picking up any sort of point on the road could yet be the difference between a place in the last eight and an early exit.
"We weren't far away, but it's not enough to be good losers," said Moffat after Edinburgh fell to their second defeat to the Blues this season.
"We made some basic errors which stopped us building pressure, and we gave away two or three daft penalties in the first half. We were lucky that Dan Parks missed them.
"At least we picked up a losing bonus point and that could prove to be vital because this group is going to be tight."