hey, thanks for your question! Botkit is mainly a conversation management framework. Botpress provides developers everything around bots development via modules.
For example you can build a subscription list, schedule messages, send broadcasts, have analytics, do A/B testing, have a built-in management interface, password protection etc. In fact, Botpress works very well in harmony with Botkit.
I would call it a complete framework (Botpress) vs a single library (Botkit)
You should build an 'app store' for bots, just like https://wordpress.org/plugins/.