When manufacturers seek to improve operations, two philosophies compete. Process reengineering calls for discarding existing workflows entirely and redesigning them around a clean-sheet vision of how value should flow, often eliminating whole categories of activity at once. Kaizen, by contrast, pursues a steady stream of small refinements proposed by frontline workers, each gain modest but compounding over years. Advocates of reengineering point to dramatic, headline-grabbing improvements-a 40 percent reduction in cycle time achieved in a single year, and dismiss kaizen as too slow to matter in fast-moving markets. Yet the comparison is less favorable to reengineering than such figures suggest. Reengineering projects frequently fail outright: a large share are abandoned before completion, and even successful ones impose severe disruption, since the radical redesign demands that workers unlearn established routines and often triggers resistance or attrition. The headline gains, moreover, are typically measured against the moment just before the project, not against the cumulative baseline that incremental methods would have produced over the same multi-year horizon. Kaizen's defenders observe that a firm improving two percent per quarter through hundreds of small changes may, after several years, match or exceed the reengineered competitor, and do so without the failure risk, because each change is small enough to reverse if it proves counterproductive. This does not establish that incremental improvement is universally superior. Where a market or technology has shifted so fundamentally that the existing process is built on obsolete assumptions, no accumulation of refinements to that process can rescue it; only redesign can. The choice between the two, then, turns less on which produces larger numbers in a given year than on whether the underlying process is fundamentally sound but inefficient, or fundamentally mismatched to current conditions.