Nothing is wrong with regular zip files. However, some people prefer to use .rar files as they apparently compress smaller, plus they give really cute looking icons that look like a pile of stacked books. I personally prefer zip files because if a file inside a zip is corrupt I find that I can still open the rest of the files. With .rar files I find that if a file inside is corrupt you either lose the entire archive, or the ones following that corrupt file. I can't remember which one it is but I know I've lost many files due to a few corrupt ones inside a .rar archive.

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi