Class.forName().newInstance() vs new

I have a class that instantiates a private member based on a value in a
configuration file.

The value is used to determine the class name.

I initially decided to use code similar to the following:

             // class name comes from property file
             String dbMgrClassName = props.getProperty("db.manager");
             Class<?> k = Class.forName(dbMgrClassName);
             db = (DB) k.newInstance();
             db.init(props);

However, a colleague pointed out that using "new" is faster than using
"Class.forName().newInstance()". So, I changed the code to the following:

             String dbMgrClassName = props.getProperty("db.manager");
             if (dbMgrClassName.equals("DB2"))
                 db = new DB2();
             else if (dbMgrClassName.equals("Oracle"))
                 db = new Oracle();
             else if (dbMgrClassName.equals("SQLServer"))
                 db = new SQLServer();
             else { // handle unrecognized
                 Class<?> k = Class.forName(dbMgrClassName);
                 db = (DB) k.newInstance();
             }
             db.init(props);

My question is: Does using if-else statements like the above really
improve performance? What is the best approach to instantiate classes
whose type you don't know at compile time?