Either vintage of ACRO comes on at Level 7. To my, um, “senior” eyes, the P2 did indeed appear brighter on startup. I*think* there have been some tweaks in the past with the 1st gen. I used a P1 last week in the SE US sun and was between 8&9 all week.
I go one up (8) on my personal carry P2. For me, I can’t see going to 10 on the P2. YMMV. Zeroing I went down one to confirm @25yds.on an indoor range.
Too bright for me draws the eye to the dot; that’s the opposite of what is supposed to be happening-looking through the sight, dot superimposed.
I have little concern over the battery life and plan to change yearly(2032).