Pasquini and Dyce are both recommended texts for OVC. I've heard that Pasquini>Dyce from many upper years because it has better diagrams!
Usually the differences between editions are not to extreme! If your really curious some textbooks list the changes they made between at the beginning of the book. They probably have the book at the UoG library (if your in Guelph over the summer) and you could check it out or borrow a friends copy, they may even have the 10th ed at the library!