The finish is supposed to be more durable than previous finishes. It is a coating, similar to ceratoke. But how exactly it compares to ceratoke I couldn't tell you. I don't holster it either.
I went with the AmeriGlo for simplicity sake. If I had gone with the base model, I would have replaced those sights with Trijicons. I really have been impressed with Trijicons. I don't have any experience with Dawson FO sights, so I can't comment on that.
The plug depends on what you want it for. If you want to keep crap out of the mag well then thats an option for sure. But if you want it to assist you leading the mag in then I don't think that it is necessary. I find it very easy to lead the mags in.