Heroku is a bit higher level. If you're using heroku, you're using their blocks and their methods of passing traffic, logging, etc. With lambda, it's just a function. You have to connect everything yourself, not you can do it exactly the way you want.
It's just code with basic function entry point. You may get your parameters and configuration in a different way, but not much else changes. There are only so many ways to call some code.
