That's an excellent question that urban planners and public works departments actually debate quite seriously. Having seen both types in cities worldwide, I can share some practical observations.
Round bins, often called "bell" or "dome" bins, have some clear advantages. Their circular design makes them approachable from any angle - people can toss trash without searching for an opening. They're generally more stable in windy conditions since wind flows around them. The dome top also helps prevent rainwater accumulation, reducing liquid waste issues. However, their capacity is often smaller, and they can take up more footprint relative to their actual volume.
Rectangular bins, increasingly common in modern cities, maximize capacity within a smaller footprint - crucial for crowded sidewalks. Their flat backs fit neatly against walls or poles, creating cleaner lines. The larger openings accommodate bigger items like food containers or small packages. Maintenance crews often find them easier to empty with standard equipment. The downside? Their corners can collect debris and require more thorough cleaning.
For most street corners, I'd lean toward rectangular designs in high-traffic areas where space efficiency and capacity matter most. Round bins work beautifully in parks, plazas, or areas where pedestrian flow comes from multiple directions. The best solution many cities adopt is mixing both types based on specific location needs - rectangular where space is tight, round where accessibility is paramount.
Ultimately, the "better" choice depends on your specific priorities: maximizing capacity (rectangular) versus maximizing accessibility (round). Many modern designs now blend elements of both, creating oval-shaped or corner-friendly designs that attempt to capture the best of both worlds.