Restore or Update to 3.0?

[mwg3c]

What are the differences between "restoring" to 3.0 and "upgrading?" Does restoring start you from scratch (i.e. you have to set up e-mail again, type in your contacts, etc)? I keep hearing that "restoring" to 3.0 is better than "upgrading" to 3.0 if your device is jailbroken.

My main issue is I just don't want to lose all my settings, contacts, voicemails, etc. Does "restoring" from a backup solve that problem?

Thanks for all the help.