CAVEAT: I am trialing Studiometry, which I do not know nearl as well as the (bug ridden and wanting iBiz and Billings). I don't know this application very well yet, so these feature remarks are to be taken "with a grain of salt" at this stage.

My biggest concern so far about Studiometry is accessing the time sheeting data; the one clear strength of Billings is that I can connect to the SQLite3 data (as .bex backup file) and perform and SQL I like to extract data, anytime, forever.