The Aug is nice but it's a mostly dated design. You get a lot more features for the money with the Hellion including but not limited to, fully ambidextrous controls and ejection port, better factory trigger, replaceable hand grip with AR style grips, adjustable gas block for shooting suppressed, etc...etc...etc...
Aside from the 80's movie nostalgia I'm not sure what the Aug offers that the Hellion hasn't improved on.
I won't get into a p---ing match with those that like the Hellion.
Saying the AUG is dated is nit-picking. The M-16/AR-15 design has been in service since 1964 but everyone seems to be either adopting/modifying it to one degree or another.
I'll just point out to those not familiar with the AUG that it has an adjustable gas system, the mag release is ambi, the charging handle is more easily accessible and also serves as a secondary bolt release (HK slap), a dual port ejection is there with the appropriate stock & bolt change, and the barrel system is quick detachable. Lastly, the trigger on the AUG can be improved with trigger pack mods which I've done.
And the AUG can be broke down into a shorter package for transport, and for maintenance faster/easier IMO.
OAL between the two is a moot point since my AUGs (both 20"barrels) are only 1.25/2.75" longer, but I'll take the extra performance with the 20" barrel for my conditions over the Hellion 16".
Stock adjustability is a moot point to me for a bullpup since a short LOP is better for when wearing gear, or hunkering up. The 1.5" adjustability with the Hellion really isn't that much compared to a AR collapsible so IMO it's almost not worth having.
Changing grips is a moot point also since the AUG angle is right for the platform.
With the Hellion, I felt the flip-up BUIS were awkward in relation to the high cheek weld, the ergos with the safety location were undesirable for me as well as the bolt release, and the charging handle location wasn't as good as the AUG.
When I say the AUG is simpler it is, and its worked for many decades for many more countries in mil-use.
If I was getting another bullpup I'd go with a MDT MDRX.
I won't say I hate the Hellion I just found it didn't work for me at various levels.
Too each his/her/its own for what works for you.