Well, Abe, the main difference is that one is made from a cow, and the other made from a pig. 
Sorry. But with an opening like that......
Anyway, there are distinct taste and textural differences. I'd say that the primary one is sausages made with beef tend to be drier and harder. Most salami, per se, is made with a combinaton of the two.
I'm not aware of any general rule that calls for more salt with pork over beef. Where did you hear that? Based on all of my references, there is no significant difference at all. Here, for instance, are some comparative meat-to-salt figures:
Kosher Salami: 5 lbs beef chuck, 4 tbls salt.
Calabrese Salami: 5 lbs pork butt, 4 tbls salt
Hard Salami: 2 lbs beef chuck, 3 lbs pork butt, 5 tbls salt
Genoa Salami: 2 1/2 lbs beef chuck, 2 1/2 lbs pork butt, 4 tbls salt
Essentially, the differences in dry sausages stem from the kinds of meat(s) used (and their proportions), the ratio of lean to fat, how it was ground, and the herbsl, spices, and other flavorings added.