I RECENTLY BOUGHT THE SIG WITH THE ROMEO RED-DOT SIGHT ALREADY MOUNTED: How to Choose the Right Handgun Red Dot Mounting System.

Thanks to a battery failure, I wound up shooting it with the iron sights yesterday. Conclusion: Accuracy is just as good with iron sights, but target acquisition — really reacquisition after the first shot — is significantly faster with the red dot. Also you can keep both eyes open with the red dot, which probably improves situational awareness.