In a formal paper, which one is more formal, active sentence or passive sentence?

I generally like to write passive sentences. But when I use Grammar to modify, he always changes to active sentences or persuades me to change to active sentences. For example, the following sentence:

Many side and covert channels have been utilized to break various
encryption algorithms to leak private keys.

There are also phrases similar to passive sentences:

Grammar’s advice is:

execution of the programs –> programs’ execution

the efficiency of CPU –>the CPU’s efficiency

the sth of A–> A’s sth which is better?

Is its suggestion reasonable?