POP3 and IMAP are application-layer Internet standard protocols used by local e-mail clients to retrieve e-mails from a remote server over a TCP/IP connection. Virtually all modern e-mail clients and mail servers support both protocols as a means of transferring e-mail messages from a server.

They are both text-based. Both transmit more or less same amount of data.

Here is the brief comparison of both:

Mail.dll supports both POP3 and IMAP (and SMTP), give it a try at:
http://www.lesnikowski.com/mail/

In IMAP protocol there are two commands to retrieve a folder list from the server.
Most servers use LIST command, some servers support XLIST command (GMail does).

XLIST provides additional folder flags such as \Inbox or \Spam (which are very useful if folder names are localized).

You can read more about XLIST here:
http://www.lesnikowski.com/blog/index.php/localized-gmail-imap-folders/

Unfortunately when you ask for subscribed folders with LSUB , those additional flags are not send by the server. There is no such thing as XLSUB command.

The only way to workaround this limitation is to first download all folders with flags using XLIST, then use LSUB to get subscribed folders and finally match the flags by name.