That's an excellent question, as keeping your outdoor trash secure is crucial for preventing messes and deterring pests. From my experience, the most secure locking lids typically feature a robust, integrated mechanism rather than a simple flip-latch.
The top contenders are heavy-duty bins with a built-in key lock or a combination lock system. These are often found in commercial-grade or high-end residential cans. The lock is usually integrated directly into the lid's handle, requiring a key or code to open. This is your best defense against determined animals like raccoons and even human tampering.
Another highly secure option is the "clam-shell" or "tuck-away" lid design with a central locking bar. These lids often have a metal rod that you twist to lock the lid firmly onto the container's body, making it extremely difficult for animals to pry open. Look for models made from durable, reinforced plastic that won't become brittle in sun or cold.
For maximum security, I'd recommend a bin that combines a physical lock with a design that has no obvious pry points. Brands like Toter and Simple Human offer models with sophisticated locking systems that are truly effective. Remember, a secure lid not only keeps pests out but also helps contain odors and keeps your property neat.