I purchased and early R9S. When the slide cracked and needed to be replaced I decided to try the sightless slide.
It is far better without sights. My accuracy, usually 7 yd, is as good or better without sights. Especially when practicing rapid draw and fire.
If I do not tip my head back to bring my reading prescription in my glasses into view, the sights are just a blur anyway, so they don't help me at all.
Instead of trying to align relatively small features (sights) you are using the entire profile of the slide. Which for defensive purposes can be very effective.
I now think I will go pull out some before and after targets to compare to see if I can see a difference.
As always, what works for you is what works for you.
Craig T.