I think we're mixing some arguments together here - and perhaps 'better' isn't the right word to have used in this article but it's the one that most usefully fits. And I'm going to make a controversial statement....
Hitler was an excellent world leader, not for the morality of what he accomplished but simply for his methodology of how he accomplished it. Had Hitler's stated aims been 'to raise the German people out of poverty' rather than 'to take over the world and murder all the jewish people in the world' then he would be studied as one of the most successful leaders of the 20th Century. We can argue that we don't like Stalin, but we can also argue he was a 'better' leader than Trotsky, even if we disagree with a) everything he did and b) his methodology. Both Stalin and Mao are still somewhat (baffling to me) revered in their homeland. We Brits still maintain a collective feeling of goodwill towards Churchill... even though, in my opinion at least, the man was an aristocratic windbag who had about 5 good years across his entire parliamentary career and caused a vast amount of unnecessary death.
Churchill would win hands down in any election of the British people if he hauled his corpse out of Westminster Abbey. That's why Boris Johnson writes books about him. When we say 'who is the better leader?' and we're trying to write an objective article, what we're really talking about IS who successfully enacted their agenda and will most likely get re-elected. Otherwise you'll end up with an article that reads.... 'Democrats believe Biden is better, Republican's believe Trump is better, do you agree?' - hardly going to fly off the Medium shelves.
If you make a promise to murder grannies in a nation full of people who want their grannies dead because 'inheritance' is the biggest issue - then you are the more electable President. If you promise to give everyone $100,000 but everyone can see you'll crash the economy and leave the grannies sitting on their untapped wealth then you aren't going to get elected.
When you remove subjective morality and see the enactment of the agenda as the pre-cursor to election/re-election - what you're doing is trying to understand the electability argument according to the other side. While you might find 'infant mortality' to be a good measure of national success, that metric might not be shared by someone who believes 'immigration statistics' is the better metric. What this article is about is trying to judge both men against their own standards (as those are the ones which matter to their core base) and make a prediction about who will be re-elected. This is as close as I can get to 'objectively better at the getting and keeping the job of President' - without letting my own biases get in the way. :o)
