> I would say there is currently no “right” or “wrong” as long as both Python 2.7.x and Python 3.x support the libraries that you are planning to use.

No. 3.x is right, unless you have a darn good reason. Darn good reasons:

1. A library or legacy codebase is in 2.x, or a system will only support it, and it is impractical to refactor to 3.x

2. You are being paid to specifically write in 2.x. Often, this is because of reason 1.

It's pretty simple, really.