Something like TodoMVC for backends would be nice... in essence, you create a backend for a TodoMVC front end, each using the same web-server platform and language and TodoMVC front end. The difference being the back end SQL server, with as much processing on the server, if it supports procedures, as possible. Maybe extending the example for a location, and a local date/time.

Using Node.js, and Angular for the server/front end, it would be easy enough to swap out the "todo-mvc-server-data" module... as long as each supported the same interface(s), it could be a good test...

Setup the same hardware for each backend, and then run performance tests against a node cluster for the front end. It would by no means be comprehensive, but would be a nice comparison point (like TodoMVC itself).