What is actually different?
Every accounting product is designed around an imagined customer, and you can usually tell who it was. FreeAgent's is a contractor: one person, a laptop, a handful of clients, work billed by the day or the project, and a tax bill that needs forecasting because nobody is deducting it at source. Almost every decision in the product follows from that person.
Bizzle's imagined customer is different. Someone whose work arrives by telephone, happens at somebody else's address, and generates a receipt in a van rather than an entry in a timesheet. A plumber, a salon, a mobile mechanic, a cleaning company. The phone ringing unanswered costs them a job today; a timesheet would be no use to them at all.
Both keep a proper double-entry ledger, and both handle invoices, expenses and VAT. The overlap is real, and it is not where the decision lives. The decision is which of those two descriptions is closer to your week.