I was on Differin, and it really didn't do much for me. I'm on Benzaclin too now, in addition to Retin-A. I seriously wouldnt use both at the same time; I used two acne medications at the same time (but these two were over-the-counter so that might be different from the result of using two perscription ones) and my face was burnt. This was the Christmas weekend, and I went into the city with my skin absolutely just peeling from my face like a bad sunburn. My family was always asking what the heck happened. This is not to say that it would be bad for your skin or with the medications you are using; different medications have different reactions to one another. If they're compatible, I don't think it really matters which one you put on first, but I would say the Differin since I was told Benzaclin was just for spot treatment.