Yet another Holywar that divides the Unix community.
A lot of time and many different tasks are spent in an editor, so often very strong beliefs are held on the inate superiority of one program over the other.
Perhaps it's a good idea to try both before picking one. I think most of the differences are subjective engineering tradeoffs, so there isn't One true editor. The only thing we can be sure of is that the Emacs binary is larger than the vi one.