Scripted quests sort of dictate the tone of the quest.. ie if its an urgent task you must drop all else and get to it. But radiant quests sort of leave you to your own devices, and because of the scant narratives involved, I find I can think up my own backstory as to why Im fetching X for Y. Radiant quests will be dull if you fast travel or do them for the paltry reward. They're really more about the journey imo.