Agile vs Waterfall: when the choice actually matters

It's rarely a religious war. Here's a practical way to decide based on uncertainty and cost of change.

The useful question isn't 'which is better' but 'how expensive is it to change our minds later?' When change is cheap and requirements are fuzzy, iterate. When change is costly and requirements are stable, plan ahead.

Most real projects live in the middle. Hybrid approaches let you plan the fixed parts and iterate on the uncertain ones — the skill is knowing which is which.