I previously wrote that for IELTS essays, one-word verbs are preferred over their phrasal verb equivalents because phrasal verbs normally sound informal.
As with many things about language, there is no hard rule for this. In fact, it often depends phrasal verb.
The ones to avoid would be those marked as INF in dictionaries (INF = informal). Others may not sound informal, and might even be preferred over their one-word synonyms, which sound too archaic even for academic writing.
An example of a phrasal verb I would use is take up (a hobby) as this sounds more appropriate than the one-word verb synonyms such as undertake, commence or start. Take up does not sound informal, and it collocates with hobby more strongly than any other verb.