An aero road helmet makes a lot of sense if you're regularly riding above 30 km/h—think road racing, fast group rides, or spirited solo efforts where you're chasing speed. These helmets are wind-tunnel tested with smoother surfaces and fewer vents to cut through the air, saving you roughly 5–15 watts at 40 km/h compared to a standard road helmet. That's a meaningful free speed boost if you're already pushing hard.
The trade-off is ventilation. Aero road helmets run noticeably hotter because those reduced vents mean less airflow over your head. On hot summer days or long climbs, you'll feel it. If you live somewhere warm or do a lot of slow climbing where speed doesn't matter much, the heat may outweigh the aero benefit.
For most recreational riders cruising under 25 km/h, an aero-informed helmet is the better call—it gives you a slight aero shaping without sacrificing cooling. Save the aero road helmet for when you're actually riding fast enough to benefit from it.