What is the difference between Capocollo and Coppa di parma?
Coppa (aka capocollo) is a type of cold cut (salume) in Italy. You'll see it with different names, including capocollo, lonza, and lonzino. They are all made from the same part of pork. It comes from the neck to the fourth or fifth rib of the pork shoulder or neck, and the name "capo-collo" means "head-neck." "Di Parma" simply means from Parma, and it means the product is created according to certain traditions from that region (though it's actually produced in other regions). The word "coppa" means "cup" in Italian. I'm just guessing here, but I suspect it may be called this because of its shape which is created when it is trimmed (it is cut to be cylindrical). 

I suspect the two products you are looking at have different amounts of fat. They are probably both delicious.