Yea, So I follow the logic of the above example and agree...However, I think MGMAT's explanations are somewhats only partially complete..for instance
Free MGMAT EXAM: "Subtropical Cyclone Question"
When describing the similarities between unlike things, the idiom "compare to" is used. When describing the differences between like things, the idiom "compare with" is used. In this sentence, differences between two like things, a tropical cyclone systems and subtropical cyclone systems, are discussed. Therefore, the idiom "in comparison with" is the correct choice.
MGMAT CAT I EXAM: "TV and Test Scores"
There are three problems in the original sentence. First, the comparison is highlighting a difference in the effect of television on children, as measured by test scores. The original sentence uses the idiom "compared to," but the correct idiom for highlighting differences is "compared with."
Reading closely, they're not contradictory. However, the 2nd explanation NEEDS to say "highlighting differences between two like things". Otherwise, the explanation is as cryptic as the question!!!