One of the big advantages I see for React is React Native (I realise there are other js native solutions but this seems like one that will really take off and take control). Nice Meteor and React Native integration would be king. Being able to use the same language for Web, iOS and Android is really nice IMO. It’s not the end of the world to be writing my Web templates in Blaze and mobile in react native though.
At the same I do think Blaze is easier to use than React. I like it’s simplicity. Although that might just be due to having far more experience with Blaze.
Being able to harness the entire React ecosystem is a plus too. And it’ll be a lot larger than the Blaze ecosystem.