"compared with" vs "in comparison with" vs "assessed in

Hello,

what would you consider more appropriate?

-“She is writing her thesis under my guidance on a topic related to the Australian tax system compared with the European one”,
-“She is writing her thesis under my guidance on a topic related to the Australian tax system in comparison with the European one”
-“She is writing her thesis under my guidance on a topic related to the Australian tax system assessed in comparison with the European one”

Thanks in advance

???

What on earth have you made a comment about or for, then?

The first and second sentences are more fluent than the third, though I would use ‘relating’ rather than ‘related’.
However, my suggestion would be one of these:
With my guidance, she is writing her thesis, which compares the Australian and European tax systems.
If the sentence is about her achievements rather than the fact that she is being guided by you, then there is no need to mention ‘under my guidance’ at all. It will be assumed that she has tutor guidance for her thesis:
She is writing her thesis which compares the Australian and European tax systems.