Runtime Analysis

I just ran a testbed of 4 types of SQL queries:

1. inline SQL with a StringBuilder
2. managed sql
3. SQL text processing (@SQL as varchar(5000); SET @SQL = 'SELECT ' + @var...)
4. a regular sproc that has the columns and table name hard coded

1,2, and 4 always end up at about the same time given the averages.
3 is always at last 1.5 times slower, and usually closed to 2 times.

1 and 2 both use StringBuilders, the code is a direct copy, and 3 is a copy as well.

My managed SQL is:
    [Microsoft.SqlServer.Server.SqlProcedure]
    public static void usp_Items_Select_Managed(SqlString table, SqlString name,
        SqlString value)
    {
        // sql 
        StringBuilder stringBuilder = new StringBuilder();
        stringBuilder.AppendFormat(
            "SELECT {0}.* FROM {0} WHERE {0}.{1} = {2}",
            table,
            col,
            value
            );

        SqlConnection sqlConnection = new SqlConnection("context connection=true");

        SqlCommand sqlCommand = new SqlCommand(stringBuilder.ToString(), sqlConnection);

        sqlConnection.Open();
        SqlContext.Pipe.Send(sqlCommand.ExecuteReader());
        sqlConnection.Close();
    }

Is there anything wrong with my Managed SQL, or is this just the way that it is?

Thanks