When it comes to being single, masturbation is just fine. You can end it as soon as you want, you can stretch it out as long as you want. You can go slow, fast, rough, softly. You can use toys, you can use your fingers, hell, you can use your pillows! And, at the end of it, you don't need to pay anyone, engage in any awkward conversations (unless you're walked in on I suppose), no need to worry about what the other is thinking, no worries, no problems.
However, if you actually are in a relationship, forget solo action, double team your genitalia!
Masturbation - I can depend on myself to know my own wants and needs and respect my gender identity in bed, which is hard to get a guarantee on from casual sex partners, and in "scratching that itch" I won't expose myself to any other potential itches of the STI variety.
mostly masturbation, but sometimes with the right connection casual sex is hot. If it's casual, it's bet if both people know it's casual. I don't like using someone for sex. I mean if I think it's casual, and they think it's going somewhere, that's not enjoyable for me.
Casual hook ups are never any good for me--maybe I've just never found the right person, maybe I'm cut out for it, but every casual counter I've had has been with a sexually clueless dullard. Sounds mean, I know, but it's true. I'd rather masturbate.
It really does depend on my mood, some nights I want sex and other nights I'm completely content with the rabbit. I'm not sure if I want a relationship or not, so I have no problem with a one night stand or fwb.