[detaro]

Less of a link to Matrix, which many of the initial adopters probably would get.

it doesn't feel to me as a stronger brand later (both are fairly random words for many people if you don't look at an explanation)

violent connotation (CNN headline: "protesters organised using the encrypted Riot app").

potential confusion in tech-y circles with Riot the gaming company (which could totally be in the market to offer a messenger, given that they run one of the biggest online games), for Vector I didn't have any other project in mind.

In the end it's just a name and it won't make or break the app for me, but I personally don't see the benefit of the new one.