I have the 20RES NG model, but when I was at the dealer last fall to purchase, I saw the RCA model. I was only there for maybe 15 minutes so most of the info I got was opinions from techs and other customers.
The RCA model have aluminum panels that can all be removed without any tools, so that is a plus if you are doing your own servicing.
The RES requires a phillips screwdriver for the right side panel, and 10mm socket to remove the front and left side.
I have never serviced mine in the dead of winter, but I would be concerned about cracking the panels removing them for service. I have no proof of this, but I would be more cautious.
Some customers in there said they have seen the paint on the RCA model peeling off in a few years.
Same customer told me that the RCA model is louder than the RES units because of the metal panels with the spring connectors and also they don't have as much insulation.
A technician working there told me that the RES model fades in the sun. I don't worry much about that as mine is located more in the shade because of the house, deck and hedges.
I am in Canada so maybe our models could be different. The manufacturing date on mine was the same year as installation so they are not older units being replaced by the RCA model. Last fall I saw both models still being made.
Again, this is just info that I got from a few people and could just be opinions.
Thought I would share my info with you.