master of this domain wrote:
The OP's question and most of the replies are overly simplistic. It sounds likes the writers know nothing about the 800 or the variety of 800 runners.
A 400-800 runner against a 200-400 sprinter will be very competitive even down to 500. Think of Juantorena (1:43.5/44.2) or more recently Emmanuel Korir (44.2).
On the other hand, an 800-1500 runner could get crushed up to 600 meters by a true 400m specialist. Think of Symmonds and Murphy: 1:42 guys who couldn't break 47 in the 400.
These are runners with similar 800 ability who differ by THREE SECONDS over 400m.
The answer to the OP's "question" varies massively.
I do not agree with you poster. If we consider 400m Olympic gold medalists elite, I cannot think of one 400m Olympic gold medalist who could have beaten Olympic 800m gold medalist from same Olympics in 600m. It does not matter if 800m gal or guy is an 800m specialist, 400m/800m person or 800m/1500m person. I would not have bet on Vince Matthews, 1972 Olympics 400m gold medalist versus Dave Wottle in 600m race. I would not have bet on Wayne van Niekerk versus David Rudisha in 600m race. Even 47-something 1:42.xx 800m specialists in your example could race at least 77.xx 600m on their 800m training. Niekerk showed up to 2016 Olympics after training as a 200m/400m man. The only way Niekerk could have been capable of sub-78 600m was to alter his training. That is a different thread. Six-hundred yards is the distance elite 400m and 800m did square off and can square off. Of course I am assuming 400m gals & guys train as 400m athletes.
Note: Elite 800m athletes do not have a statistically normal distribution if we use statistic terms. You offered two 400m/800m men and you offered two 800m/1500m men as examples. There are fewer elite 800m athletes whom are elite 400m & 800m athletes versus elite 800m athletes whom are elite 800m & 1500m athletes. There are three 800m guys with sub-45 F.A.T. 400m & sub-1:44 800m. One-forty-four 800m is roughly equal for women to 1:57 800m (percentage away from world record). Forty-five 400m is roughly equal to 50 400m for women. There are only about seven women with sub-50 F.A.T. 400m & sub-1:57 800m.