This is always one of those interesting questions to me. Everyone is different and Every dog is different. Each has thier own fun way of delivering pleasure and a great experience.
For me, I think I generally prefer a large dog for overall companionship including the sexual moments. I like the simple and fun way of playing that leads up to the actual mating. I like being a pet owner and I like the lifestyle. Some of the downsides is I can be open about it, but that is why I come here.
Humans are different. It is nice to get a massage or have a good conversation or go out for drinks. That is something I cans to with my Shepard. The right human can also be very fantastic in bed. I like that too.
For me, the best combination is for me to live alone with my dog and enjoy that lifestyle with a casual human relationship on the side for the times I want or need something different. Smile