cPanel has its own File Manager but any web based file transfer/managing utility isn't going to work as well as one that runs on your computer.
FileZilla is a free ftp client that is reliable and stable. You can download it at:
http://filezilla-project.org/
For those needing something with a little more power, I use and recommend IpSwitch WS FTP Pro. It's quick, stable, and reliable.
