In the last month, I posted this picture of a three round group shot with my rattler at 50 yards using a Holosun 507 in circle only mode.
I don't see any difference in my groups with a circle versus a dot. I do find a dot easier to shot call with. The circle works great in low sun angles because it is not subject to splatter like a single small two moa dot.
On the 507K, which my wife runs in circle only mode on her 365 EDC, the circle eats batteries quite a bit faster than a single dot.