Babydoc posted a VERY long post about all contraceptives about 2 years ago. It's still on the servers if you search.
Pills are 99% effective if used properly. Withdrawal has a roughly 8% failure rate, so if you practice both simultaneously, you should be .01 x .08 = .0009 or 99.91% effective although I think that 99% is good enough.
The best contraceptive to date is the Mirena IUD, with a failure rate of .01% It is good for 5 years and costs around $650 to insert if you don't have insurance. The hormone is NOT systemically absorbed so there are no effects other than NO PERIODS (YEAH!!!!!) after 3-6 months.