Gyros and IMUs are often selected based on static datasheet parameters such as Noise Density, ARW, and Bias Stability. In real-world control systems, this approach is frequently insufficient. Systems that appear stable during laboratory testing may exhibit jitter, drift, or instability under dynamic, cyclic operating conditions. This article explains why thresholds, recovery behavior, and deterministic timing – rather than averages – are the factors that truly define stability in advanced control loops, and why IMU selection must be treated as a system-level decision.