I would suggest Node due to the fact that you are already using Angular which means you get to work with JavaScript on both the front end in Angular and the back end in Node which can simplify things as even if you're good with two different languages it is still a bit more difficult to jump back and forth between the two than it is to work with only one. Additional points to be made are that Node is fairly popular these days so there is ample opportunity to get support from the community as well as being able to continue using it into the future because it will still be popular when you go to start the next project or perhaps if you are looking to get hired I see a lot of positions that are asking for Node at the moment. Another option and I say this because I have been learning it recently is Go. It is increasing in demand and it is a wonderfully powerful yet simple to understand language that can be used for many purposes. They definitely got a few things right when they created Go and I am enjoying my time learning it and hope to put it into use in the near future.