The language SDKs themselves are roughly on par with one another (with a handful of exceptions that we're actively working to address). As you note, however, the packages are where the biggest differences remain.
https://github.com/pulumi/pulumi/issues/2430 is on our backlog. The goal here is to enable cross-language package sharing.
Until then, I'd recommend erring on the side of the Node.js SDK if you want to leverage libraries like AWSX.