How do I find out what features are supported and which I'd require something like Babel for?
node.green is a fairly new resource that focuses on more releases of Node and also utilizes the Kangax test suite, but they don't list results for older versions of Node.
That's why I built whatdoeslambdasupport.com, a website to quickly see what tests pass or fail for each Node runtime that AWS Lambda supports.
The tests results are generated by running the Kangax tests inside each of the Node.js Lambda runtimes so there's no "it works on my machine" issues with the test results.
You can use this resource to determine what JS features you can use in your Lambda projects, or to make a call whether including something like Babel makes sense.