eh, my computer has assigned entourage as the default email client and i hate it! Entourage is so slow, and it never tells you what its doing. You click send and it will freeze up for 2 minutes while it does something, and then when you try and close it 15 minutes later it says that there is a network operation in progress. Ive always had problems with microsoft email programs though. When i was with windows I couldnt use outlook, I just find them so slow and clumsy. Besides, the security flaws in outlook (not sure about entourage) are incredible. Microsoft has just left the back door wide open.
I use Mail. Its just so simple. You drag attachments into the compose window, type in the text, then click send. As soon as an email arrives you get the ping noise and a little number on the dock icon telling you how many unread emails you have. And because apple are stingy and only give you 256 meg of ram with your iMac, i prefer to use mail because it doesnt use nearly as much processing power as entourage. I just leave mail running in the background so as soon as i get an email i can read it, and i dont see any perfornance differences.
Spam wise, i never get spam anyway, so i dont know. Even my hotmail account rarely gets spam. I think its a case of prevention rather than cure. Never just throw your email about.
Set up wise.. I change ISPs alot, so my isp email address changes alot. And with microsoft email clients changing your account is next to impossible. There is no simple way to manage, delete and add new addresses. Mail has a little list of accounts, with delete add and edit buttons. the only real problem is changing outgoing email servers, i cant seem to delete any of the servers off the list.
An email client should be small and simple. Entourage is an unnessaarily big program and is just too slow and unreliable for me to use. I used it for a little while, but it was just terrible, and when i saw the sent date on one email as "tommorrow" (i have a screenshot to prove it) i decided to change to mail.