Periodic tasks - organization

>What can you say about these two approaches? Which would you recommend
>and when?
If the task is inherently periodic (updating a wall clock display, for
instance), use the simple periodic form. If the task responds to some,
not necessarily periodic, event, then program it that way. The only
legitimate reason to force the program into an unnatural form would be if
some so-far-unmentioned constraint (e.g. other interfaces to the task,
or performance, or management decree) required that.