This is why you see so many porn videos where the performers have to finish themselves off with their own hands, even in straight porn. I know I've been in real sex situations where I was having trouble cumming, and it's not because of any fault of my partner's technique -- it's because real sex requires you to be VERY INTO your partner to be enjoyable; there's just not as much in the way of perfect timing and perfect touching that another person can deliver. Even an actual asshole or mouth wrapped around my dick can often not provide as much genuine physical stimulation as my own hands.

Real sex is about the person you're with and the idea of them getting down and dirty with you, which is the most crucial part of being turned on and wanting to cum .... being enamored with the thought of another human being doing all this naughty stuff with you. That's the driving force behind cumming when you're with a partner.

Now, on your own, you can focus more on really maximizing physical sensations and you have the luxury of finding an erotic story, porn video, or even a mental fantasy (I still do that all the time), and sometimes it's just easier. Some of the most intense orgasms of my life were wrenched out of my dick all by myself with no other real people around.

I can certainly cum much more quickly on my own -- I just know where all the mental switches are. I'd be curious to hear some feedback from other people about that. Is there anyone in the world that cums quicker, faster, and more intensely only when they're having real sex with real people? Do most of you find that it's easier to cum (at least in the pure functional, mechanical sense) all by your lonesome?

But rule of humb, real sex much better and more more memorable.