There is no such thing as a "best setting" for task type. The task type is
a switch you use when editing work assignments so when you change one of the
Work, Duration, or Units variables, Project will recalculate the proper
other variable in the triad. As such, the task type setting for a given
task might change many times as you refine your plan dependong just what
term you're changing and why you're changing it in this particular edit.
Example: I have Joe Painter assigned to paint a room. He works an 8 hour
day, is assigned 100% to the task, and we estimate it will take 5 days to do
the painting. Work = Duration * Units - always, it's Project's Prime
Directive and you can never, ever, have a task that violates it. So his
100% committment to 40 hours (5 days) of painting means that task requires
40 man-hours of effort. Now we're about to edit his work assignment to 50%.
When we do, we have to ask ourselves just why we're doing that. Is it
because we need him free'ed up some of each day to do some other work
elsewhere at the same time the room is being painted? If that's the case,
the painting will still require the same number of man-hours of effort but
the duration it takes to do that will be twice as long. Make the task Fixed
Work, change the Units and Project recalculates the duration and sets it to
10 days. Or the other alternative is we have realized it's actually only a
20 man-hour task but we don't need it done any sooner than 5 days
none-the-less. While usually you'd want to get it done ASAP, let's say for
some reason this time we want to leave it at 5 days. So set the task type
to Fixed Duration, edit the Units, and this time Project will recalculate
Work and set it to 20 man-hours, or even more logical, set the work to the
required 20 man-hours and Project tells us we only need the painter at 50%
committment so he can do other stuff part of the time.
The identity Work = Duration * Units is just like any other linear equation
Y=mX+b. Its terms include a constant, an independent variable, and a
dependent variable. You can pick any of the 3 terms and make it the
constant by way of choosing the task type, take your pick one of the
remaining two terms and edit it, making it the independent variable, and
Project will recalculate the third, dependent variable, term for you.
