Indoor or outdoor zapper—what's the difference?

Outdoor units (Flowtron, GOOTOP) use high-wattage UV bulbs and an open grid that's loud and bright; they're built to be hung outside. Indoor units (Buzbug, GeckoMan) use lower-wattage LEDs, quieter grids and enclosed designs aimed at kitchens and bedrooms, and they're far less effective at outdoor distances.