Title says it all. 2 multiline fields both set to be appendable. How do you compare them to see if they are the same or different.
what exactly you want to compare?
latest change? - then you can use regular actions, just like for a field without history
whole history? - then you will have to get whole history track by Lists.asmx web service method GetVersionCollection and implement comparison logic on your own
Retrieving data ...