Your guess is as good as mine.
As a personal preference, I like the "security" of panties. They make me feel sexy, comfortable, and put-together. G-strings on the other hand, are both uncomfortable to wear and whorish to look at (Hey, this is just me! Calm down, girls). It makes me uncomfortable that so many men are obsessed with them. I think they are one of the grossest things a woman could wear. I mean really. Butt floss? That's what turns you all on these days? Yikes.