Code should be easy to understand.
This is the most important guiding principle to use when deciding how to write code.
Fundamental Theorem of Readability
Code should be writted to minimise the time it would take for someone else to understand it.
To understand the code means to be able to make changes to it, spot bugs and understand how it interacts and fits into the rest of the code.
Is Smaller Always Better?
Generally - the less code is needed to solve a problem, the better.
This doesn’t mean to write dense one-liners, as minimising the time to understanding is a higher goal.