Of the various options (text-to-speech, concatenated messages, pre-recorded messages and near-real-time recorded messages) what is the best way to present information?
This depends on the type of information that you have, the number of different possible conditions and your desire (or need) to have operators on duty. Concatenated messages often offer the best of both worlds, the convenience of text-to-speech with the sound of a human voice. Many systems use various combinations of these options in their systems.