Train from Krakow to Wroclaw: times, details and fares in English on the official Polish railway website: https://www.intercity.pl/en/ Bus is a bit faster but traffic is always unpredictable. Times, details and fares in English on: https://en.e-podroznik.pl/ If the time difference is less than an hour I'd always choose train over bus because of the traffic aspect.
Przemyslaw Thank you Mary, I was asking about transport to Wroclaw, not Warsaw. Trains seems to be slower than bus, but buses use highway that may have traffic problems especially on friday evening
Mary My apologies for misreading. :-( I do know the difference between Warsaw and Wroclaw! You're right about possible traffic delays. At least you can be pretty sure trains will run on time and they're not much slower than the buses on this route.