> Advanced Natural Language Processing Tools for Bot Makers – LUIS, Wit.ai, Api.ai and others (by @bashmakov)

Our personal preferences goes to Wit.ai from Facebook and LUIS from Microsoft – as they have all necessary elements for building conversations and they are free. At least for now, so you don’t have to worry about the price.

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For the end-to-end solutions that you can use with less code, we think Api.ai is the way to go. If you need the embedded capabilities as well so as not to depend on an internet connection at all.

Alexa Skills Kit is proprietary for Amazon Echo devices, therefore, you can’t use it with arbitrary bots at Slack or Facebook Messenger for language processing, but it is ideal for smart home bots that augment your kitchen or living room environment, and which are built specifically for Alexa.

IBM Watson will work smoothly in an enterprise environment when you need to feed large amounts of data, and you have a decent budget and want to have a reliable and proven service provider behind you.

It seems that Microsoft is splitting various functionality into various services each of which have a different quota of free transactions and then charge a separate fee under the umbrella of Cognitive Services:

https://www.microsoft.com/cognitive-services/en-us/pricing

LUIS is my favorite! Microsoft Cognitive Services also integrates with LUIS very easily which gives you speech recognition too.

Interesting overview. I had a similar article bookmarked with a good review of Wit.ai and Api.ai, among other platforms:
https://tryolabs.com/blog/2017/01/25/building-a-chatbot-analysis—limitations-of-modern-platforms/