I've never liked the belt-only look, as it's completely superfluous without the trunks. Unlike Batman's utility belt, there's no functional reason for having a belt if there's nothing for it to hold up. At least the Snyder design had an interesting aesthetic purpose, and helped to break up the empty space. The muted colors Snyder favored also helped.
I'm really glad Gunn decided to go with the trunks, though. Superman's probably the only character that can still pull off that look, unless it's a period piece.