Personally, I see it as a grass is always greener scenario. When you’re in a relationship, you get companionship, regular sex, a partner in life, and you get consistency. On the other hand, when you’re single, you have more freedom, more money, a more flexible schedule, you can have sex with as many people as you want (or can, I suppose). There are benefits and drawbacks either way. I enjoy being single, I enjoy being in a relationship. I see it as a lateral move. One is not better than the other, they’re just different.
Just my take, I suppose it depends on what you want out of life. For some people, one may be preferable to the other.