Ditto the above. This is the simplest/easiest way to compare trim levels for any given model year. The only drawback is they only list Ridgelines back to 2011:
Since you didn't list what year you are interested in, it is hard to answer correctly. I had a 2011 RTS that I added the stock RTL fog lights to. Perfect fit. There was a couple of other stock upgrades I did also.What are the differences? Some parts for RTL do not work for RTS or RT.