I just started working at a local HD dealer in sales. They have 2 used 1300s in stock. Nobody knows anything about them. The '06 I think is definitely a Retro, but the '05 looks like a Retro, but has spoked wheels.
as far as I know the R is the retro and has cast wheels. The S is for spoked wheels I believe. I think this is the only difference. I could be wrong, but this is the only difference I've heard or seen. Hope this helps!
I would have to say they are pretty even. Some guys love the spoke looks and others like the cast wheels. I like the cast wheels because they are was easier to clean! The spokes are really cool looking, but I kinda see half and half. I think on this site I may actually see more guys with the R model. Maybe they just speak up more or maybe I'm just not seeing all the posts. I don't think one is highly preferred over the other, just my opinion.