Having been through 3 classes with low-light shooting involved, I'd say that at CQB distances, to about 15 yards, not much difference.
It's one of those things that it's better to have it and not need it, than vice versa, but as a non-leo, there are not too many instances I can think of where I'd be able to indentify a person (and identify them as a threat), but not have enough lighting to see my sights. I much rather have a flashlight. During the classes, when were did use flashlights, I had no more trouble picking up the non-tritium sights vs. those that had them.
Suffice it to say, I believe a good flashlight is a must have, especially as twilight approaches. I can probably do without the night sights, but I wouldn't toss them if I had them.