You should choose a one-day hiking backpack based on the features you need. For short hikes where you only carry the basics, around 15-20 litres is good. For longer trips, about 30 litres hits the sweet spot. For a full day in the backcountry, 35 litres or more may be necessary.
Aside from the volume, look for hip and sternum straps to help distribute the weight. A padded hip belt could also make the hike more comfortable.