In the mean time if you read the description for the various resource gathering ships it should tell you what each ships optimal range is. Additionally the travel times for each ship per sector tile are as follows-

Small / Regular Harvestor - 4 min per sector tile.
Cargoship - 3 min per sector tile.
Freighter - 2.4 min per sector tile.

Also keep in mind that they all spending 30 seconds loading / unloading for each trip.