Amazon's Alexa assistant has one major advantage over the Google Home (and other competing voice assistants) - the massive amount of third-party skills. Google has a similar developer platform for Assistant, Actions on Google, but the simple fact that Alexa has been around longer means it has a more sizable collection of abilities.
Amazon announced today that Alexa has over 10,000 skills available, with a 3x increase since just September 2016. I'm sure many of those are unfinished experiments from developers trying it out - for example, Amazon is giving developers a free hoodie just for publishing a skill.
Still, this shows Alexa is definitely a growing platform, and should help convince OEMs to include Alexa in their products. Google has some catching up to do.
- Amazon Developers