RS has 20mm longer headtube (in the 56cm frame) than the R3. It also has about 11mm longer chainstay to compensate the taller headtube to achieve the same riding control as an R3. RS would be a bit more "comfortable" than a R3 because of these difference: you are more upright because of the taller headtube, and you feel a more plush ride because of the longer chainstay. But make no mistake, RS is not a touring bike, it's still a race bike. There are suggestions that you can just add a bunch of spacers and flip the stem on a R3 to get the same effect as RS, and they are wrong! The geometry change in the taller headtube *requires* the chainstay lengthening. And if you jack up a R3, you will get a twitchier and very different ride than a RS.

I also believe the new R3 has a different seattube diameter from the RS, but I could be wrong.