I did the hero arc in Atlas Park, but I hated doing it, with its heavy population right around the statue of Atlas and the venders there and Ms. Liberty. So I created a gold-side toon. People said that the Gold side was tedious and hard, but I did not have a problem at all and enjoyed the arcs there. I especially like the way your toon enters Paragon in Talos and you get that "track your double" arc. I like how some of the mid-level content is somewhat tailored to your Praetorian (if you have one).
There was not a red-side (track down your double) equivalent when I had a Praetorian cross over to Rogue Isles, though and was quite lost.