I use LoopBack because it is:

• It is truly and Unbelievably Extensible
• it is default integrated with OpenAPI (Swagger) Spec Driven REST API
• I write lesser codes, because most of the user stories have been covered using the code generation
• It's documentation is more compact and well detailed than @{ExpressJS}|tool:1163|
• It is very easy to learn, hence you can build a basic Rest API App in minutes
• It has built in NPM packages required to build my Rest API which saves me time on installation and configuration
• The Datasource/Service/Controller concept is just Brilliant (that's mostly all you need to get your app speaking with an External API services)
• The support for SOAP and Rest API services is amazing!