Not sure what you mean by "the famous train"? Are you talking about the historic steam train, or the ordinary service trains?
I have done it both by the historic train, and the combined boat+train package. The river trip was magical. Fortunately it was good weather and we sat on the deck drinking wine watching the views slip past, trying to spot the railway viaducts and suchlike. Not sure that I would have enjoyed it nearly so much on a rainy day though. It was an early start, but they served a good breakfast on board. The return was by service train, for which they issued tickets as we disembarked.
The historic train trip was out on a service train, and back by the historic train. It took quite a long time to book this trip at the main station enquiry office the day before (I don't think it could be booked online). Fortunately the lass spoke good English but unfortunately she had great difficulties finding the ticket on her computer. Unfortunately the steam loco wasn't running that day, but it was still worth it even with a diesel hauling the heritage stock - much better views than with the modern stock. I seem to recall an end balcony you could stand on and watch the views slip away behind you. I also recall that it included refreshments, and a refreshment stop at one of the intermediate stations.
For the historic train, the journey out on the service train in the morning was quite pleasant. However, for the river trip, the return by service train was very different. The train was absolutely covered in graffiti, both inside and out, which made looking out the windows hopeless, and the train was heaving with standing passengers.
While in Porto, I would also recommend exploring the metro, and seeing the remnants of the old narrow gauge steam railway it replaced. And perhaps taking the metro over the Eiffel bridge, and walking back over for the views. And of course a trip on the historic tram, a visit to the tram museum to see the fish tram, and perhaps a walk along the seafront beyond the current terminus to the old tram terminus (the rails were still in situ when I visited).
There is a lot to see and do in Porto, and I would certainly recommend a stay there. My first visit was for work (signalling the metro), but I managed to get my stay extended to include a weekend sightseeing. I went back several years later to see the results of our labours, and still left feeling there was more to see. I seem to recall that there was a longer river trip available, that went much further up the river, but you had to return by boat, at least to Pinhao. If I return to Porto, this would definitely be on my bucket list.
