I get a little confused when people just list them as moonflowers as there is a morning glory (I. alba) and a datura (datura inoxia) variant... among others.

Either way, both can become invasive if you're in it's hardiness zone, and 7a is pretty close, but moon flowers, like morning glories, have seeds that can lay dormant in the ground for several years before germinating and I think that's what really gets people's goat over them in terms of being invasive. You've decided you want something else in that area and you're fighting seedlings for the next several years.

Personally, I love them and put them in several locations where I can either maintain seedlings (around a tree) if I get tired of them, or out in the back of my property where the only thing they'll fight/crowd out is poison ivy and other types of invasive vines.

As for appearance, I can tell you that the morning glory variant has very distinctive heart-shaped leaves once it gets it's first set of true leaves as do most morning glory vines. <shrug>