Some VERY good discussion here and food for thought for my next trip to the range. I am a FS shooter but I agree with the thought "if I have time to aim, I will close my left eye. If I don't have time, I will keep them both open." I desperately need practice on my quick draw for the surprise defensive use. But if I am practicing for score, I contend that I will continue to use the method that feels most natural to me.
Thanks for all the video/instructional links - very enlightening!