POP and IMAP email accounts

In Snow Leopard, the email account creation assistant created POP email accounts automatically. When I upgraded to Lion, these accounts remained at POP. However, when creating new accounts for the same ISP, the assistant created IMAP accounts. For exactly the same email addresses and ISP, my iPhone creates POP accounts. The result (I think) is that, after synchronising my iPhone in Itunes, I end up with two email accounts for the same email address and ISP - one POP and the other IMAP. Is there a reason behind the creation of two different accounts?

Do both of the accounts work? I would think that only the POP account would work, and maybe it defaulted saving them as IMAP instead of POP.

Both the iMAP and POP accounts work although I haven't quite figured out the behaviour patterns of downloading mail messages yet. As far as I can see, it is not possible to save the accounts as POP rather than IMAP - I have tried everything but trying to force the system to accept a POP account when it would normally have created an IMAP one has proved ineffective (my ISP is btinternet.com) but different results may occur with different ISP's.