Which do you choose? POP3 or IMAP?

POP3 holds mail on the server until the user can retrieve it.  Once downloaded it is no longer available on the server. This is a fine choice if you will only retrieve your mail from one place.

IMAP allows emails to be accessed by a client but continues to hold the email on the server.  This is useful for accessing your emails from more than one source, such as your PC, networked PC's and mobile devices.

Peacockes Hosting recommends the use of IMAP.