There's some differences. Technically, with mdk the node and keys are on your infrastructure, not ours.

We spent a lot of time focusing on the developer experience for mdk. When a developer thinks "I want to add payments" the products they pick up are very full featured. They don't just get the credit card network send / receive API, they get a lot handled for them. To me this is the biggest difference, you don't need to know anything about Bitcoin to get a checkout page and get paid.