What is the difference between the Integrated true-mode stimulus application (opt 460) and the Differential and I/Q devices application (opt 089)?

The Integrated true-mode stimulus application (TMSA) and the Differential and I/Q devices application (DIQ) both simplify measurements of differential (balanced) devices. The two applications however, are used for different measurements.

TMSA (460)

Handles measurements where the input and output frequencies are the same.
Ideal for S-parameter measurements
Can get forward ad reverse sweeps in the same channel
Measures both differential and common-mode S-parameters
Not used for IMD or harmonic measurements

DIQ (089)

Used to measure I/Q modulators/converters and differential mixers.
Used for harmonic measurements of differential amplifiers (THD and IMD)
S-parameter traces must be defined explicitly. For example, S21 must be defined as b2_F1/a1_F1.
Forward and Reverse sweeps cannot be done on the same channel.