Personality certainly matters. But it might be more useful, in terms of the actual stakes of a contest, to think about the presidential election as a race between competing coalitions of Americans. Different groups, and different communities, who want very different — sometimes mutually incompatible — things for the country.
The coalition behind Joe Biden wants what Democratic coalitions have wanted since at least the presidency of Franklin Roosevelt: government assistance for working people, federal support for the inclusion of more marginal Americans.
As for the coalition behind Trump? Beyond the insatiable desire for lower taxes on the nation’s monied interests, there appears to be an even deeper desire for a politics of domination. Trump speaks less about policy, in any sense, than he does about getting revenge on his critics. He’s only concerned with the mechanisms of government to the extent that they are tools for punishing his enemies.
If you’re an American, and you like what the Democratic coalition is after, then get involved, help with money if you can, and pay attention to downballot races too, not just the top.
Two parties working together to carry out whatever they feel like (e.g. full support of genocide) against the will of the people (and having a media machine trying to convince people that it’s what they want) isn’t much different from having a single figurehead acting as dictator. In fact it allows for plausible deniability.
Would the Holocaust have been better if it was carried out between two political parties where you get to choose who carries it out? Vigilance against fascism should include being able to identify when a system is fascist in a roundabout way.