From previous conversations on HN, wasn't the problem that to use What3Words, you have to use their online proprietary system? and thus won't work offline and make you dependent on their service?

Plus Code seems to just be encoded Gps coordinates which seems far easier to integrate.

W3W is proprietary, has commercial aims (you can purchase short-codes), cannot be used offline, is completely dependent on the provider, and a simple transposition of words will result in somewhere completely different.

Simply using lat/lng or one of these deterministic systems (geohash, plus.codes, etc) is a far superior option for something to be adopted globally.

This thing is beyond terrible. Just tried it. It's auto picking my browser language instead of English. The choice of words is terrible, I don't know how to spell half of them, I can't imagine anyone able to write them down or understand them over the phone.