[sellyme]

There's two scenarios here. Either you're looking up an exact location (either w3w or ll) as the information is required and then communicating it to others, or you're doing that in advance for an area you're familiar with and then memorising it.

In situation A, it's going to be a lot quicker and clearer to communicate w3w than an ll pair (for the same precision a ll pair requires 12-18 digits, plus specificity on +/-).

In situation B it's going to be a lot easier to remember the w3w descriptor, and you still have the same advantage as in situation A.

For spoken communication, w3w's rival is "it's 123 Fake Street, I'm the bloke in the green parka", not ll pairs.