Almost always top, but...with the right man and the right personal lubricant, it can be such fun. Although, the only man who fucked me and I well and truly wanted it to never end was my ex. His cock is the most perfect cock I've ever experienced. Sucking it or riding it, I don't think I'll ever experience the wealth of sensation his cock provided.
As for you JBisme, I think you're a top. Your lean build and long straight cock is the hallmark of a man built to pound and ass long, hard and deep.