They are "roughly" equivalent, but the adult FS tests are much less demanding than their standard track counterparts.
I don't think honestly with the way they currently are that the adult MITF tests are "easier", at best they are slightly restructured. The moves tests actually all have at least one element from a higher level test - that technically makes them harder than standard track (though they are arranged in a way that may make them easier for some adults to test). However on the flip side, when you finish the adult moves and go on to test intermediate moves, you've already tested two of those patterns, so it makes that test slightly easier to train for, in comparison, because you only have to learn 3 more patterns (and the passing standard is the same between gold and intermediate at 3.0 for each pattern, so it should not technically be judged to a higher standard).
I've opted to start over with adult track rather than stay with standard track since I end up having to take the same number of tests to get to the same place - even though I took pre-pre in 1996 it doesn't put me at any advantage because you have to test one level higher in standard track to match the adult track tests (because of those moves borrowed from higher level tests).