Why ZIP, and not JAR???
First off, yes, I do know that JAR files are preferred for Java programs. However, I ran into several problems as I was writing the code.
The main problem was the ability to write (or lack thereof). Java programs that run from JARs can read the files packaged inside the JAR. However, they CANNOT write. There we have a problem: That means the program can't write your scores and settings to the JAR. [Think about a read-only high score table].
I had two solutions to choose from: write to the user's home directory, or not use JAR. The problem is that I wanted the program to be portable, so the scores and settings would go where the program goes. So I went with the latter choice.
A JAR is essentially a ZIP with Manifests and some other features. So the compression would be the same - same load on the servers, same download time for the users. ZIP also accomplishes my goal of making the program portable - if the program is unzipped to a flash drive, your scores/settings will remain on the flash drive from computer to computer.
I personally hope that the ability to write to JARs is created in Java 7, but for now, ZIP will have to do.