Journey planners are handy if you don’t know which service or operator to look up.
Journey planners are clearly more useful for non routine, unfamiliar, complex and multi modal (e.g. train and bus) journeys.
Ideal for route planning and assessing alternative options.
First Bus have a personalised bus journey planner which can be printed to pdf or printer and can be printed in large format.
But if you are looking for a simpler tool the mobile route planners are generally easier to operate as are the embeddable route planners. E.g. the transportdirect tool is compact and effective.