RAR Password Finder is a .RAR password cracker for Windows. This is a very basic application that only uses one attack method. It uses brute-force to guess the passwords of RAR files with password-protection. This is a program that is considerably lighter than other solutions and it is extremely intuitive.
Zip Password Finder is a brute-force cracking tool for ZIP files. The application is similar to RAR Password Finder. If it weren't because one can crack ZIP files and the other RAR files, I would say they are identical. In terms of functionality, it seems like RAR Password Finder is better equipped.