Squeak,
based on the research (anicdotal, not scientific) we were told that the system keeps the house and a more even temperature and for longer. i.e. there is less problems of the first floor being boiling and the second floor cold.) We were also told that the operating cost could be less. It also had the advantage of being quiter, i.e. no loud noises in the middle of the night when the system kicks on because it’s cold and the steam escapes from the valves. There is also always a potential problem when changing boilers in a stema system that the change could create knocking noises for which there is basically nothing that can be done. We kept the steam system and had a good plumber install it and did not have knowcking noises (although the plumber did not guarantee that it won’t happen) If you are only changing the boiler, keep in mind that you will have a new boiler with 80 year old pipes. At some time those pipes will need to be replaced.