MIchaelW is right!!!! Buses are cheaper but a lot worse than trains, plus, you can saver the night in the hotel by taking sleeping trains. I did that this summer in Poland (although trains and accommodation was really cheap in any case) and was great... taking the train in one place, sleep there and wake up in the other side of the country!!!!
YOu can also combine both trains and buses as you like it! Is only another suggestions. Interrail is a good option if you are planning to travel around an area for at least 22 days. More info on: http://www.interrail.net/