Platinum based chemo and monoclonal antibodies cannot be compared to each other. One can be used as a mono therapy, the other not, one has cancer killing properties, and the other prevents cell replication but does not kill the cancer cells. They are definitely complimentary therapies, and when used together optimize the outcome.
http://www.oralcancerfoundation.org/treatment/targeted_therapies.htm Just as some chemo makes the cancer cell more susceptible to radiation, targeted therapies hold growth and replication rates down so that other chemo and radiation therapies can do their jobs. The most successful treatments are often "cocktails" of a combination of elements to produce the optimum end result.