You're right. I had to go back and look (which is sad since I've had half a dozen Atlas rails). Logic has 7 sides of MLOK vs. Atlas 3 sides MLOK and 4 sides of lightening holes. Which is basically what you said above after re-reading it. The MLOK vs lightening holes is where the weight difference probably comes from I'd guess.
Well I ended up buying a 11.5” 5.56 Logic upper on Arfcom so I figured I’d do a quick side by side with my 10.5” 300BLK w Aero R-One.
As we suspected, they’re practically identical. Logic has 7 sides of MLOK and no lightening holes on the top rail.
The R-One has 3 sides of MLOK and 4 sides of double stacked lightening slots. It’s also actually 0.02” thinner side to side and top to bottom while looking at the front of the rail. If you look closely, in front of the R-One’s QD socket, you’ll notice a small step-down at 3,6,9 o’clock positions. So I’m sure the R-One will be negligible lighter, so if every 1/2oz counts, got with that one. Lastly, the R-One’s 3 and 9 o’clock sides are not perpendicular to each other, they actually taper inward from bottom to top ever so slightly. I only noticed this while measuring with my calipers.
Otherwise finish is the exact same and once you throw rail covers on, they feel the same in the hand. Same material thickness, same top rail design aside from the R-One’s lightening holes, same attachment system, same overlap of the receiver/alignment system
One call out on my Logic upper, I noticed that the pinned gas block on this Hanson barrel is slightly canted and therefore only about a business card’s thickness away from contacting the handguard compared to about 3-4 cards’ gap on the opposite side. Minor issue IMO.