So what was the Pony Express news?

Slow. To say the least.
Not as slow as the boats from England to America at the turn of the 19th century.
Anyway, the telegraph was invented and although at first no one knew what to send through the lines, the Civil War changed all that. Send news of battles. So suddenly people in Massachusetts could find out almost immediately what happened in a skirmish in say far-off Virginia. Especially the names of those dead and wounded.
Overnight, news began to be published using the telegraphed, Morse coded stories.
In the West, the pony express was still the primary source of news and information, but only until the late 1800s when the lines arrived.
No one relied on horses after there were telegraph poles.