These get compared as if choosing one means giving up the other, but they're not actually rivals — a K-map is built directly from a truth table's data, just rearranged. The real question isn't which one to use; it's what job you're doing at the moment.
What a truth table gives you
A complete, unambiguous specification: every input combination, its exact required output, nothing left to interpretation. It's the ground truth every other representation — canonical SOP, a K-map, a minimized expression — has to agree with. If a problem is stated as a description ("output 1 whenever the input is prime," for instance), a truth table is usually the first thing you build, before any simplification technique touches it.
What a K-map adds
The same information, rearranged so that adjacency becomes visible — which is the one thing a plain truth table's row-by-row list doesn't show at all. A truth table tells you exactly what the function does; a K-map additionally makes it visually obvious which rows can combine into simpler terms. That's the entire value-add: same data, but organized specifically to make simplification possible by eye.
When a truth table alone is enough
If the goal is just checking or communicating a function's behavior — not minimizing it — a truth table does the job completely on its own, with no need to rearrange anything into a grid. Verifying a circuit's specification, documenting expected behavior, or a function with too many variables to fit a practical K-map (see How Many Variables Can a Karnaugh Map Handle?) are all cases where the table itself is the deliverable.
When you actually need the map
The moment the goal shifts to minimization — finding the smallest circuit that implements the function — a K-map (for 2-6 variables) earns its place, precisely because it turns "which rows can combine" into something you can see rather than something you have to calculate row-by-row. Past 6 variables, Quine-McCluskey takes over the same job algebraically, covered in Quine-McCluskey vs. Karnaugh Map.
Using both together
In practice, most real work starts as a truth table (from a specification) and only becomes a K-map once minimization is the actual goal — which is exactly the workflow the Truth Table to K-Map converter is built around: enter the table, watch the map and minimal expression build themselves from it automatically.