I like platforms that show you some shop status past its completion. I don't like cleintsmart, because as soon as you submit the shop, it disappears into oblivion and you never know what happened to it. Prophet is one step up, where it goes to your completed shops list, but is never again updated to show it has been checked, accepted and paid. Sassie allows for status updates, but it depends on the company. Some companies are better at marking shops completed, received and paid, and some are worse. I only shopped for one company using Clientsmart and they were showed all the different stages that my shops were in. I really like that.
From the proprietary sites, I really like Second-To-None and CoRI. Again, mainly because they show exactly where my shop stands.