Someone else's touch on my dick feels better than my own. That's true all over my body, and may be related to the reason why we can't tickle ourselves, only others can. That phenomenon is still not fully understood, even today, but I believe has to do with how our brains process the feedback loop of our own touch.
As for jacking, however, I also agree with wrestlervic, that manual masturbation usually works better with my own hand. In that case, the feedback loop works to my advantage, because I know when I need to change speed, grip, etc. I can tell the other guy what to do, but that can be clumsy & disruptive, and requires a patient partner.
Last point, though: when I'm doing the other guy, I always use a good lube, and some techniques I've learned over the years, that have had quite a few declare it the best hand-job of their entire lives. Whether oral or manual, I consider giving pleasure to another guy an art form.
Referring to wrestlervic again, the idea of "just doing a job and trying to get it over" is anathema to me. I just don't like cock, I worship it, and I hope I always reflect that when I have sex. Job hell -- it's my passion & delight!