One strength of the msm is that it has supporting experimental research.
For example Glanzer and Cunitz experimented the distinct stores within memory by getting participants to learn a list of 10 words with varying lengths. They remembered more the first words (primacy effect) and more of the last words (recency effect) than the middle words due to serial positioning.
This means that the 3 components of the MSM are different, the STM and LTM are unitary and independent.
This shows the the MSM makes valid suggestions about the function of memory.