Last night, Jamie Dixon (whose book you should buy) talked about his experience at Build this year. His main takeaway is that Microsoft is pushing their Bot Framework pretty hard. Jamie showed how to create a stock lookup bot and deploy it to Slack using F# code and an Azure account.
Based on my (extremely) limited knowledge of both, it seems that the Facebook bot platform is a bit easier to deal with, as there’s a user interface for writing messages and tokenizing, but right now, Microsoft’s platform is a bit more customizable and developer-friendly. What’s particularly interesting about both of these is that the analytics and intelligence engines are both closed-source—neither company will let you see the wizard behind the curtain.