Who knew this could invoke quite a controversy! Everyone I have talked to has a different opinion and I found quite a few heated discussions online about the difference...
Unfortunately most of our original plaster walls have been messed with. The dining room has paneled boards up against the framing where the plaster and lath use to be. We decided to gut the living room (there are only three walls since one wall was removed and replaced with a big metal beam) to see what was in there as it would give us a feel for the rest of the house. It's a north facing room with two exterior walls so we knew we could beef up insulation while we were at it.
I think it was the right choice! We were able to remove a lot of nest materials, stinky mouse poop, a mouse skeleton, and see that there was no insulation at all. We also found out that way too many joists were cut up for plumbing and that we should enforce the structural integrity of quite a few of them.
So now we have to decide how we want to finish the walls and where the tv and new gas fireplace should go and where we want lighting switches and wall outlets and overhead and/or wall lighting... Lots of decisions. There is a plasterer in town that I am going to call for a price and see how it compares with the rest. Overall, this is going to be an expensive room (second to the bathrooms and kitchen) but I am hoping that we will love it once it is done and we definitely will be spending a lot of time in the one warm room in an otherwise uninsulated house!
Here are some links for the plaster vs. wallboard discussions...very interesting!