Depending on the shape of the umbrella, it can provide great shade but no airflow. If this is the case, you'll be hiding from the sun but still overheating. An umbrella with ventilation can provide you with fresh air in your little shaded environment so you can cool down more comfortably. Unless you're looking for a beach sauna, you'll want this feature. However, if you are using a traditional T-shaped umbrella, none of the airflows will be blocked and this feature will be unnecessary.