"I prefer incompetent evil to competent evil"

[The Right Honourable Martin Brian Mulroney PC CC GOQ]

Like you pointed out, this comparison is normally used in comparing Trump and RDS. I'm automatically skeptical of it, because even if it is true, it's clearly used to advance a political agenda/viewpoint. I mean, the idea of the other party's people getting worse over time is a very convenient and effective narrative, it's why we saw a certain kind of Democrat being nostalgic and almost sympathetic about Bush during the Trump years even though they almost certainly hated Bush during his presidency too. You also see this from the right, although less commonly - Republicans lamenting how much worse today's Dems supposedly are compared to Bill Clinton, although they would probably hated Clinton in his day too.

Anyway, it's actually a hard one to answer. If I accept that one person is incompetent and evil, and the other is competent and evil, who do I prefer? On one hand, incompetent evil is going to be, well, more incompetent at implementing their evil. On the other hand, incompetence at the highest level of power is an evil in its own right.

I'd go with competent evil only because I reject the idea that any politician represents "pure evil", as in everything they do will inherently have devious motives and horrible outcomes. But if I were to accept that both the incompetent and competent politicians being compared were evil to the core and incapable of doing any good whatsoever, I'd go with incompetent evil just to minimize damage

Edit: To clarify the "no politician represents pure evil" thing - no politician can represent pure evil in a system of strong checks and balances, because the worst excesses of human nature are limited by those systems. In a dictatorial or tyrannical system things are different, I wouldn't extend that sympathy to Hitler or Saddam Hussein obviously.