[kylequest]

Authy is much more complicated to setup compared to Duo. In my TFA app experiments quite a few people had problems with the setup process (failing to complete it in several cases). They were pretty technical people too, which says a lot about Authy's usability...

[chimeracoder]

There are also a lot of security concerns about Authy that were raised a while back. If you read the comments, it doesn't instill a lot of confidence in the team to implement a secure platform of this sort[0].

Unfortunately, security is one of the few areas in which 90% isn't "good enough" - all you need is one point of failure for an entire system to get compromised.

[0] https://news.ycombinator.com/item?id=4921684