Gun coatings?

Has anyone shipped there gun off to have it coated? What type of coating did you use?
I've been looking around and can't find any real interpretation on the differences, one says it's better than the other(ceramic-NP3-hardcrome) and vise versa. I'm looking at the NP3 from Robar, they say the contact areas need-not be lubed, looks high dollar though> Do you get what you pay for? I would prefer tan color but black would suffice.

I was wondering is there a reason behind coating? I like the finish on my guns just fine, But if the coating makes them preform better, let me know please,,,,,,,,,,,,,