Script Functions for Item Changes on Transactions

I have a Client Script that updates transaction columns when the line is updated.

It would seem that I can use Field Changed Function to check for a field on the line item being changed (and this will run the script on the active line and update it), or the Sublist Changed Function - which I think triggers whenever anything is changed on the Item List, and (in my script) will loop through all transaction lines and run the script on each line.

I am testing the various scenarios where Item values change (adding lines, editing lines, copying lines, updating quantities, price, price level, cost etc). In nearly all these cases the Field Changed Function appears to work satisfactorily. I am questioning the need for the Sublist Changed Function (I assume it was implemented as a 'failsafe' to try and pick up any lines that weren't updated correctly).