Good question lol - right now most of the work I'm doing is in Python or React, though I have projects in PHP and Angular as well.
The steem-js lib for the frontend and the steem-python lib for the backend is likely the best combination at the moment for developing steem apps.
Sounds familiar, except python.
I'm checking out the js lib at the moment. Whats your experience with it at Vessel so far?
It's worked great.
JS is not my favorite language, but steem-js hasn't contributed to that. It's had every API call I've needed thus far.