AR Platform I use either a 25M or 50 yard BZO depending on available ranges. The 25M is generaly good out to 220 for within 1-2" POA/POI, the 50 is good for 300 roughly...
You should remember that "red dot" style sights were originated for the military for CQB. The military has learned in Iraq and Afghanistan that most engagements happen in less than 75 yards. Thus most "red dot" style sights have no magnification. I sighted in my ACOG at 50 yards. If I ever had to use it in anger at a distance greater than that, I would just aim a little bit high! "Red dot" sights are not really intended as a target sight, they are a heads up both eyes open sight. Put the red dot on the bad guy and apply slight pressure on the trigger, job done. I zero my iron sights at 100 yards. My 65 year old eyes don't focus very well past that distance anyway.