Write when you want to:
•Make sure there are no misunderstandings
•Have constant reference to subject matter
Writing is effective in communicating with any audience that is capable of reading and comprehending your compositions. If the person ever has a question regarding the subject, they can always refer to what is written.
Make a presentation when you want to:
•Give a more detailed description
•Command the attention of an audience
When making a presentation or presenting material to an audience, it is possible to give someone who may not fully understand your message solely from reading, a more broad perspective of the matter.
Speak with an individual when you want to:
•Earn a higher level respect and confidence from that individual
•Create an atmosphere of mutual trust
For myself, speaking with someone individually, is very effective in the sense of having one on one communication with that person ensures that there are little to no distractions.