Always use newest version.
that is not so, especially with python.
Everything "newer" in computer world, is buggy, lack of help, lack of tutorials, lack of libraries
A basic example of this is:
if i am a gamer that plays minecraft, and I only care about vanilla minecraft, i dont care about mods or texture packs, and want the latest updates and featuresi can use the latest version of minecraft. However, if i am a person that uses texture packs and mods (which i am), i have to wait for those mods and texture packs to be updated to the latest version ebfore i update my minecraft version, which in minecraft can take from a few days to a few months, for some mods maybe a year.
Span this example out across a couple decades and you have python. Some people use libs that require the older version that is not yet ported up, and some dont.
the same goes for any language, some people have updated compilers for c++ which allows use of c++11, which gives them one output for an error, while others have an older compiler that gives them another output for an error, different versions, differnet uses, etc.