The Catawissa Moxie is $18 a case at the bottling plant, so $30 for a case in Saco isn't that bad (I was charging $25 a case when I made 2 trips in April that essentially paid for my gas to\from the plant).
I think the Catawissa Moxie uses a little bit less of everything. It tastes more subdued than either of the alternatives. Not as sweet, and certainly not as bitter. It's something I can drink even when it's warm, which is not something I can say about the Orca or Coke varieties.
The only difference between the Orca\Cornicopia Moxie and the Coca Cola Moxie (other than the bottle\can difference) that I can discern is the cane sugar\corn syrup. The Orca doesn't have the same cloying mouthfeel that the Coca Cola version has.
(*note: I can't seem to find the corroborating evidence to suggest this is actually the case, but bear with me for a short story.)
Supposedly at some point in the soda jerk days when Moxie was still popular, the formula was tweaked to either increase the amount of genetian root extract (the thing that gives Moxie it's "distinctively different" taste) or cut the sugar levels of the drink. This had an adverse affect on it's popularity. I think the Orca\Coke uses this stronger ratio than the Catawissa version does.