What is better for text reading and writing?

What is better for text reading...

         TextAsset content = Resources.Load("tempTextFile") as TextAsset;
         string tempString = content.text;

or Using System.IO operations

         using (FileStream fs = new FileStream(path, FileMode.Open))
             {
                 using (StreamReader reader = new StreamReader(fs))
                 {
                     string tempString = reader.ReadToEnd();
                     reader.Close();
                 }
                 fs.Close();
             }

The thing is that I need to write back in to the file as well.... for that I eventually have to use System.IO operations ... or is there a way in unity libraries for achieving that as well?