German computer magazine iX has a very good article about the new Debian Installer. Its author Holger Levsen first reports about new features of the d-i and then reports about the preseeding feature. In the last part of his article he compares preseeding to FAI and explains the difference very well.
His conclusion: “Although the release candidate 2 of the Debian Installer is still another pre-1.0 version, it is a large step in the right direction for the Debian project. Smaller deficiencies and weaknesses are still present, but concern only few use cases. In all, the Debian Installer brings a simply usable, versatile and automizable Framework for installations, which can be adapted easily with little training.”