I had uni stage 1+ for a few weeks before going stage 2. Like someone else said it depends on how available 93 is where you live. Where I live, you can get 93 at any gas station, but 91 is only available at sunoco. So the choice was obvious for me. Plus im sure 93 tune squeezes a few more HP out of the car than the 91 tune.
edit- OP I see that you are in NE PA.. How far are you from Allentown area? You should definatly check out CBTuning. He is a good dude, does good work for really good prices. Link to his page is in my sig. He is a UNI dealer too.