I can’t help with the difference between Italian and the others, but the difference between ‘regular’ and ‘Dutched’ is that the Dutch is processed with alkalai, which changes the pH. Most of Rose’s recipes use Dutched. You can always tell the difference by reading the label, as Dutch will either say ‘Dutch processed’ or, in the ingredients, it will say ‘processed with alkalai.’ It gives a deeper chocoalte flavor and something else flavor-wise, too, I forget what. Regular usually says ‘natural’ and will not have anything about alkalai or Dutch processed (Hershey’s is an example, and there’s an organic brand with a bear on it, also).
To make a perfect world and easy decision, if you can get E. Guittard Cocoa Rouge (Sur La Table carries it), it’s excellent! It’s Dutched, and it has a high fat content, so it won’t contribute dryness to your product. As a note, it’s not good to go off the label for fat contents and such, because the quantities are so small they’re not really useful to extrapolate for quantities used in baking—but I can guarantee the E. Guittard is fabulous! A lot of folks also like Droste, which is supposed to be very good, but I have not tried it.