I took the BAM a few years ago, between Komsomolsk and Tynda. Is utterly boring. The towns are nothing, is just forests and frozen lakes. The stops are very short (less than 10 mins) so you never have time to leave the station.
The confort is mostly the same, even the BAM has brand new trains, Irkutsk is worth to visit plus the aereal view of the Baikal Lake. Fly between Ust-Kut and Irkutsk, there are two daily flights, and they are pretty cheap. and then keep on the BAM. You'll also loos many other interesting cities, as Birobizhan, one of my favourites in Russian Far East.