An extra short trail is designed for quick stops such as at a service station on a road trip. Extra short trails will only have two or three suspects.
Short trails last 10 - 30 minutes and are designed for walks, hikes and exploration.
A medium sized trail is just what is sounds like, just designed for a nice walk.
A long trail can last a while. If you choose to go on a long trail, expect to be out for minimum of an hour.
It's recommended that you only go on an extra long trail if you are planning to have a murder mystery trail as the only thing you do on the day you do it. It may take multiple days depending on when you start the trail.