Predicting marathon time

Hi all,

What do you find is the most accurate race time predictor?

Strava?

Garmin?

Runna?

Manchester will be my first marathon and need to enter my predicted time. This is what the various apps say:

Strava - 4:15

Garmin - 4:02

Runna - 3:50 (😂)

Have any of you found any of them to be reasonably accurate? Does it really matter what you put in?