my guess is unless the two differ in available styles, size of dots, interchangeablity, or if one happens to have a longer half life and guarantee, then it is a toss up... I would look at the construction for durability as well, and go with the one that has the most features and is the configuration most familiar to me. I have thought about nite sites and would think that the three dot system could be more easily confused than a post in the rear and a dot in the front. it could get confusing with three dots out there in the blackness, but a vertical bar and a dot would be pretty repeatable and easy to work with....if I get one on my hunting pistol for poor lite that will be the ticket for me. If it is strictly darkness defense, I like a flashlite and or a laser on my defense weapon, the laser is the fastest and has a deterrent effect on the intended target, that should be considered.
returning to the nite sights, I would not want one that can be seen from the front and it could definitely give you away if a cuprit is behind you...
Just some considerations to ponder. bottom line for pure defense, it is 1. laser either under mounted or grip mounted; 2. a really brite light attached to the weapon that can pulse or stay on; or both..
the laser in the grip does not affect holstering and is not obvious and can pulse, or be constant on, and where it is hitting is where the bullet will go.. i have taught women safety first then use of the laser mounted to a weapon and the progress and learning curve were phenomenal and confidence was way up really quickly... that may help some..
good luck practice well and cut no corners with your protection of your own life..
dk