If I am looking at the times correctly, I looks like less time than the trains.
Generally, in Poland, buses do tend to be a bit faster than trains. There are exceptions, of course. A little cheaper, too.
Trains are considerably more comfortable and relaxed, especially if you are larger or older. Train stations are generally more pleasant than bus stations. Even if it takes a bit longer, I would pick the train over the bus every time. The extra time and cash is worth the extra comfort to me.
If you're in a hurry, though, or if saving a few złoty is a serious matter, then you might prefer the bus, especially, like I said, you are young and petite, and don't mind hanging out it a seedy bus station and having a less comfortable and relaxed journey.
Different courses for different horses. Depends on what is important to you.