Prior to the new highway we always took the ferry from Istanbul to Bandirma .Not alot to say other than the ferry is very clean and comfortable and takes just over two hours.
No idea about the train as I travel on my chariot.
Hi. If you are offered the choice, carefully select your seats on both the train and the ferry. The train is painfully slow, with no alcohol, and expensive food. At the ferry terminal, people rush off the train to the ferry, we had no idea why. We soon found out. On the ferry, you are given seat numbers, which can be awful. Most people sit where they want to until the person with that seat number turns up and claims it. We had awful seats going to Istanbul, but on return trip we spilt up and sat where we wanted to. At least three times we had to move until we found un-reserved seats and had a very pleasant trip back. Try to get seats on the upper deck, downstairs is cramped and full of screaming kids. Good luck