One advantage spreadsheets have over notebook is that you don't have to do the maths. Also you can know immediately how much each person owes or needs to get. But there is one catch with spreadsheets. You need to log in to your machine (or google id if you are using google docs), open up the spreadsheet and make an entry. But it often happens we cannot make the entries immediately. It because either we are busy or on the move. This ultimately leads to the same situation you have with using notebook where the whole group sits together trying to recall each and every bill and making entries. There is also this odd probability that you may find some bills getting duplicated.
Beezang offers you the flexibility of adding bills from a variety of medias like twitter, mobile and email. Everytime you enter a new bill you can opt to notify your group members about the bill details and more importantly Beezang keeps everyone in the group upto date about the standings so you guys settle up when the amounns owed or expected to get becomes significant.