I have used XS big dots in the past and liked them. I currently have a set of Ameriglo Pro Series Operator night sights and LOVE them. I feel as tho I can get on target just as fast as big dots.
I second the XS Big Dots they are very easy to use in a low light situation and day light as well.
I also like the Ameriglo Operators too even though I have never had them. I am not a fan of the 3 dots that are the same color as it seems to be hard for me to pick them up and focus on the front site. YMMV