For me it also depends on the task - I never do a strict TDD - but often I like to start with some tests.

Sometimes it is hard to write the tests, but it is easy to see if your code works - sometimes it is easy to write the tests, but not the code.

I would call it 'do first what is easier'.

But it is important to write the tests quickly after you wrote the piece of code - so that you don't forget something.