It’s best to keep the leaves. Although the plant as a whole likes sun, the fruit (squash) does not need it, and might actually get sunscald from too much sun, since it had been used to being shaded. Also, when you cut a vine, there is always the chance that diseases will enter via the wound. The leaves are the way the plant makes food for itself, which helps gather energy to put into its fruit. So, as long as space in your garden is not an issue, the more leaves, the merrier!
It’s best to keep the leaves. Although the plant as a whole likes sun, the fruit (squash) does not need it, and might actually get sunscald from too much sun, since it had been used to being shaded. Also, when you cut a vine, there is always the chance that diseases will enter via the wound. The leaves are the way the plant makes food for itself, which helps gather energy to put into its fruit. So, as long as space in your garden is not an issue, the more leaves, the merrier!