When designing experiments, it is helpful to know what you are designing them for.
What is the best task design for functional MRI?
It turns out that the "best" task design depends upon whether your goal is detection or estimation.
That is, the best experiment for detecting responses (i.e., to answer the question "where in the brain does the MRI signal resemble my task timing?") is different from the best experiment for estimating the timing of the brain responses (i.e., to answer the question "what is the time course of brain responses to task events?").