Which is faster and safer : loop on insert method or passing list of object

As Performance wise which is more better :

1-First :

 public int Insert()
        {
            int affectedRow = -1;
            using (IfxConnection con = new IfxConnection(ConfigurationManager.ConnectionStrings["sh"].ToString()))
            {

                StringBuilder cmdTxt = new StringBuilder();
                cmdTxt.Append(" INSERT INTO shedule(day,short,name,depcode,studycode,batchnum) VALUES (?,?,?,?,?,?) ");
                using (var myIfxCmd = new IfxCommand(cmdTxt.ToString(), con))
                {
                    myIfxCmd.CommandType = CommandType.Text;
                    myIfxCmd.Parameters.Add("day", IfxType.Char);
                    myIfxCmd.Parameters.Add("short", IfxType.NVarChar);
                    myIfxCmd.Parameters.Add("name", IfxType.NVarChar);
                    myIfxCmd.Parameters.Add("depcode", IfxType.Integer);
                    myIfxCmd.Parameters.Add("studycode", IfxType.Integer);
                    myIfxCmd.Parameters.Add("batchnum", IfxType.Integer);

                    if (con.State == ConnectionState.Closed)
                    {
                        con.Open();
                    }

                    myIfxCmd.Parameters[0].Value = ((object)this.DayId) ?? DBNull.Value;
                    myIfxCmd.Parameters[1].Value = ((object)this.ShortName) ?? DBNull.Value;
                    myIfxCmd.Parameters[2].Value = ((object)this.Name) ?? DBNull.Value;
                    myIfxCmd.Parameters[3].Value = this.DepCode;
                    myIfxCmd.Parameters[4].Value = this.StudyCode;
                    myIfxCmd.Parameters[5].Value = this.BatchNum;

                    affectedRow = myIfxCmd.ExecuteNonQuery();
                }
            }
            return affectedRow;
        }

---

THEN :

           foreach (Day a in days)
            {
                affectedRow = a.Insert();
            }

---

OR

2-Second:

public int Insert(List<Day> days)
        {
            int affectedRow = -1;
            using (IfxConnection con = new IfxConnection(ConfigurationManager.ConnectionStrings["sh"].ToString()))
            {

                StringBuilder cmdTxt = new StringBuilder();
                cmdTxt.Append(" INSERT INTO shedule(day,short,name,depcode,studycode,batchnum) VALUES (?,?,?,?,?,?) ");
                using (var myIfxCmd = new IfxCommand(cmdTxt.ToString(), con))
                {
                    myIfxCmd.CommandType = CommandType.Text;
                    myIfxCmd.Parameters.Add("day", IfxType.Char);
                    myIfxCmd.Parameters.Add("short", IfxType.NVarChar);
                    myIfxCmd.Parameters.Add("name", IfxType.NVarChar);
                    myIfxCmd.Parameters.Add("depcode", IfxType.Integer);
                    myIfxCmd.Parameters.Add("studycode", IfxType.Integer);
                    myIfxCmd.Parameters.Add("batchnum", IfxType.Integer);

                    if (con.State == ConnectionState.Closed)
                    {
                        con.Open();
                    }
                    foreach (Day a in days)
                    {
                        myIfxCmd.Parameters[0].Value = ((object)a.DayId) ?? DBNull.Value;
                        myIfxCmd.Parameters[1].Value = ((object)a.ShortName) ?? DBNull.Value;
                        myIfxCmd.Parameters[2].Value = ((object)a.Name) ?? DBNull.Value;
                        myIfxCmd.Parameters[3].Value = a.DepCode;
                        myIfxCmd.Parameters[4].Value = a.StudyCode;
                        myIfxCmd.Parameters[5].Value = a.BatchNum;

                        affectedRow = myIfxCmd.ExecuteNonQuery();
                    }
                }

            }

            return affectedRow;
        }