You a non-native English speaker? I'd have thought the letter X would have made Alexa and Bixby hardest to pronounce for most people, and Siri and Cortana the easiest. Spanish stress pattern for 'Cortana' doesn't match English, making it harder to say it in a way that it recognises. But that's obviously just me - I'm Scottish, and none of these things have ever recognised a single word I say.

One of the most-requested features on these smart assistants would be the ability to rename / nickname them, but that's an expensive ask. They all offload their actual voice processing to a cloud server somewhere, and then have their 'activation sounds' hard-coded into them. Needs to be either a few syllables in a row (hay-see-ree) or some unusual sequence (bicks-bee) to not have hundreds of false positives. Giving them nicknames would require them to send their voice samples to their back-end servers basically 24/7, which would cost them a fortune to run. And also be a privacy nightmare, but I'm sure the operators would be just fine with that if they could afford it.