i was actually out testing between the Athlon Argos, Helos, and Ares earlier today. I was in the same boat and wanted to see which would be best for me, so I ordered all 3. I'd like to state that this is my opinion and I think scopes are more of a personal preference. If i have to look back and forth between two scopes 5 times at the same target to determine which is better, then the extra $1000 isn't worth it. and I'd rather spend that money on something else.
i was comparing them looking at a target at 1150 yards i thought all the Athlon scopes did well. The Ares was definable clearer then the Argos and Helos, but not by much. Color wise i think they are about the same. Granted i was looking at a field of dead grass so there wasn't a lot of vibrant colors this time of year. The Ares was brighter overall with that slight edge in clarity. With all three scopes i could see the wind blowing grass next to the 1150 yard target, and read the mirage.
As far as function i like the fact that Ares goes from 4.5-27x, also the turrets were much nicer, had crisper clicks, and had more MOA per revolution. The Helos has locking turrets which is nice, and a Christmas tree reticle similar to the Ares. The one thing i noticed on the Helos is that the elevation turret clicks felt soft and not as defined, but the windage turret was loud audible clicks that were super crisp. It was a large difference between the two, which is odd as you'd expect them to be the same. I even pulled the cap off the elevation turret to clean all the excess grease out as i have seen in some reviews. While this helped the elevation turret wasn't nearly as good as the windage. I wonder if this is a common problem or if Athlon could fix this?
The Argos turrets were okay. The one thing that sorta drives me nuts on the Helos and Argos was that there was "slop" in the turrets. so once you set them on a number, you can actually wiggle the turret back and forth so it looks like you are in between ticks. but you can wiggle the turret and know which tick you were on. (its a bad description of the issue but not sure how to explain it exactly) I have a Nikon scope like this and it is dumb and sort of annoying. However, your only paying a few hundred for a scope so can't be that picky. Ares wins in turret category.
Oh and one thing i noticed is the eye relief was the same on the Argos and Helos, but the Ares was noticeably longer. Almost too much it seemed. I'm a tall guy and its possible that with out a picatinny it would be hard to move the scope far enough away from my eye. But then i guess you don't have to worry about scope eye.
Overall i was impressed by the three scopes. For me I think I'm gonna keep the Argos. I'm putting it on an AR for hunting. The glass seemed the same as the Helos, it has the same amount of elevation travel. The only thing the Argos lacks is the locking turrets (which isn't a big deal to me) and it doesn't have the Christmas tree style reticle. The Ares was by far the nicest. Clear glass, really nice turrets, and has the same reticle as the Helos (except the reticle lines on the Ares are thinner which i preferred).
If i was building a long range bolt rifle, or wanted to use it for competitions then i would buy the Ares. It was a really nice scope and i would choose it over another Vortex PST since it is $200 cheaper, and i think performs just as well.