Druid or Shaman

I'm coming back to the game..again. Previously, I had dual boxed a warrior/shaman, but I became annoyed of switching between the two characters. I really just prefer to play 1 character. However, I don't have SoD yet, and I don't want to spend $40 on the expansion until I'm sure I'll be sticking around for a while. So, between Druid and Shaman, which is a better soloer? Correct me if I'm wrong, but both are valuable group members, so I shouldn't worry about that, right? I was leaning towards druids because people have always bragged about their soloability. I'm just looking for some advice, and could someone lay out the general solo strategies for these 2 classes please?
Thanks in advance.
Thanks in advance.