Every person responRAB to products differently.
You may be one of the blessed who sees great results with the antibiotic and Differin, or your acne might be more stubborn. The only real way to find out how it will work for you is to try it and see what happens.
If those two don't work, the next step is probably Accutane (depending, of course, on what you have already tried)...and any responsible dermatologist won't prescribe something that hard core until they see you have exhausted all other possibilities.
Good Luck!