I think it depends on the company you are working with. I appreciate Sassie because it is so easy to upload receipts into it.
What I miss with Prophet is in signing up for shops, the ability to see what is out there whether I am eligible for it or not. With Sassie I often take a look at all shops in my state with 1 keystroke because if the company is shopping a particular client in other parts of the state it is likely they will be shopping that new store here that hasn't opened yet. I also like being able with 1 keystroke to see nationwide whether the company has any shops posted and then look at a few to see if what they are paying is comparable to what I expect to see for such shops.
While Prophet lets you self assign and request to be a backup, you never know if you aren't seeing shops you are 'ineligible' for because they have nothing or because you actually are 'ineligible' due to age, income, education etc.