Questions on red dot optics

[Eternal Viligance]

I've got a long gun I am considering scoping, and I have been told that for a quick shot in low light conditions a red dot scope is a good idea. In addition to the red dots, what other kind of scopes are good for a quick shot in low light situations? There are some terms I've heard tossed around that I'm unsure of the technical meaning, for instance "illuminated reticle" (is this as simple as it sounds?) could anyone enlighten me as to its meaning? Also, (this may be more general to all scopes) is there any significance to the diameter of the optic and how it affects the general use, i.e. does a large diameter optic have any advantages over a smaller one? I also understand that there is a great range in the price of the red dots, does anyone have one they like that isn't too expensive? The Leatherwoods seem to be pretty inexpensive, does anybody have any warnings about them? The Truglo red dot also is inexpensive, does anybody out there have any experience with those? Thanks