Well, in my opinion, there is a reason they call them back up iron sights (BUIS), because they are back ups.
I've got an aimpoint on my PSA, and an eotech on my colt. What is best? Well, it is all about have options.
G19 G26 G30 Sig 2340 357 Beretta U22 (kid's) Two Saiga 12 Two Draco 7.62x39 "pistols" Colt 6920 Saiga SGL21-94, M92 Krinkov "pistol," PSA Patrol Carbine Saiga 223