Last night Joe Biden and Donald Trump squared off in simultaneous town halls, Biden on ABC and Trump on NBC. Neither was heavily watched on broadcast, with Biden slightly ahead. However, the Hollywood Reporter notes:
The NBC-Trump town hall was simulcast on MSNBC and CNBC, which will likely add a few million viewers to the total in the final ratings out later in the day. (This story will be updated when they become available.) There's a good chance the aggregate viewership for the NBC special will end up with more viewers, though ABC is likely to retain its lead in the broadcast-only numbers.
In other words, ratings comparisons will be somewhat “apples and oranges” as NBC has the cable news outlets while ABC does not. Expect each campaign to tout whichever metric - aggregate or broadcast-only - makes them look stronger.
Later ... Updated figures show 13.9 million viewers for Biden, 13.1 viewers for Trump, though we are cautioned these are not the real "final" numbers. A difference of 800,000 viewers in a nation of 330 million is more or less irrelevant, it is something like 0.2% or 1 out of 413.
Later still ... The more-or-less final numbers are these:
All told, Trump came out on top with the most viewers online and on TV combined — with 17.8 million views versus Biden’s 16.8 million.
This means roughly 10% of Americans had a look at one of them. Put another way, ca. 90% of us couldn't be bothered.