We chose MongoDB because in our testing it is much faster on performance. It also is very flexible with its document-based DB that does not need a relationship. Also with the SDK its very each to build interfaces and create CRUD functions. Also, it can be deployed and ran anywhere instead of only one specific cloud provider making us more cloud agnostic
Stripe was made with developers in mind first so the extensibility of it is great! This makes it very easy for us to integrate and automate as much as we need with its APIs and SDK. It allows a lot of customization of exactly what we need to build our applications. They also manage all of our customers from a tax and accounting perspective which makes it easy from a business standpoint.