Go with the AUG.
I am the proud owner of an AUG A2 and I couldn't be more pleased with the rifle. If the US versions are on par with the Austrian made Steyr AUG than they will beat the pants off any competition hands down.
Just holding an AUG you notice right away the difference from the beauty of its balance to its ergonomic feel as you shoulder it.
I've never fired an FN SCAR L or H, but I can tell you that it will be hard pressed to beat the AUG in terms of felt recoil. The rifle really just snugs into your shoulder when you fire it with very little muzzle rise. I've never had a problem shooting sub 2 MOA with my AUG. If you mount a 3x scope like an ACOG on it you'll hit what you aim at no problem.
Do ya like to wear gloves? Ever need a rifle in a SHTF winter event? The AUG has a nice wide open hand gaurd that accepts gloved hands, which is a plus.
How many military units field the FN SCAR of the SIG 556? How many field the AUG? Combat tested and proven under every condition in every climate on earth.
The AUG really sells itself once you fire it.