The highest noise margin is offered by

Noise margin is the maximum noise voltage a logic gate’s input or output can tolerate without its logic level being misread. It is derived from the family’s guaranteed voltage specifications as NMH = VOH(min) − VIH(min) for the HIGH state and NML = VIL(max) − VOL(max) for the LOW state, with the smaller of the two quoted as the family’s noise margin. A family whose output swing is large relative to its switching threshold therefore ends up with a larger noise margin.

Applying this to the four families using their standard voltage specifications:

Because CMOS’s complementary p-type and n-type MOSFETs switch fully across the supply rails while ECL deliberately restricts its swing to gain speed, CMOS ends up with the largest swing-to-threshold ratio of the four — and this rail-to-rail swing is a fixed, single-technology property of CMOS, unlike BiCMOS whose swing depends on the specific process used.

This matches the standard CMOS-versus-ECL design trade-off: ECL is chosen when raw switching speed outweighs noise immunity, while CMOS is chosen when low power and noise robustness outweigh speed, confirming CMOS as the family with the highest noise margin among the four.