Several factors should be taken under your consideration.
1. Wind speed. It is the most significant characteristic of hand dryer products. It seems like that water on hands is evaporated by the wind. But in fact, the fast wind blow away the water to dry hand. The wind is like a blade, or Airblade, which is a concept brought out by Dyson. The blade shave water off hands. So the wind speed is a key factor, but not the only key factor. Hand dryer airflow depends on the motor power, and is the product of wind speed and cross-sectional area of air outlet. So if the airflow is limited, reducing the outlet cross-sectional area could increase wind speed. But drying time wouldn't decrease. Further more, if wind speed is too high, hands may feel painful. As AIKE's opinion, the airflow should not be less than 30L/s to achieve good drying performance and the wind speed should not be greater than 120m/s in case of diminishing using experience.
2. Drying time. Actually, the definition of drying varies from person to person. So it is hard to measure accurate drying time. Hand dryer suppliers always claim a drying time section. Customers can choose according to their own needs
3. Economical and Power efficiency. Hand dryer is more economical and environmental than paper towel. In public places, in a year the saved money with using hand dryer than paper towel, can buy a hand dryer itself. Generally, hand dryer total power is less than 2000W and heating power accounts for a large part of that, which might be a big burden for home electrical grid. So Aike provide a switch for customers to control heating module to minimize power when heating is not necessary.
Of course, excellent design and quality should be your concern too.