All of my pistols have Tritium 3 dots. The standard ones but with white outlines. That way if/when the Tritium stops working, the sights will still be usable by the white circles. Standard lifetime on the vials is 10-15 years. Although some have lasted 20 and one gun I bought new already had a dead front when I got it from the dealer.
The big dots are good for folks that really have an eyesight problem. I'm not that far along yet.....
Unless you are shooting bullseye, there's really no need to have sights at all. Pistols are really for close range work and Cowboys seldom used sights. They learned by using instinct and practiced a lot.
Alan - ANYTHING I write is MY OPINION only.
Certified Curmudgeon - But, my German Shepherd loves me!
NRA-Life, USN '65-'69 & '73-'79: RM1
1911's RULE!