Regarding the current Biden/Trump situation, I would bet on Trump because the chances for either of them winning are closer to 50/50, while the outcome odds for Trump are above 2.0 everywhere.
50/50? Why do you think that?
The first election was very tight and he disappointed many of his voters during its mandate.Although it's true, I'm going to quote @STT here, because it is entirely in accordance with my thoughts on the matter:
~50/50 is how I'd rate odds in a cautious way normally the sitting president might be said to have 60/40 advantage but this year being a fallout and we presumed a negative for Trump then at least it would seem even odds towards the challenger. ~
I placed my bet on Trump, and if I lose it, so be it. But overall I think it's a right strategy to bet on something that is less likely to happen, but not that less likely as the potential winnings differ.