There is one aspect of Sara that is better than Siri, and that is its ability to understand written questions, rather than only spoken ones. So if you are in a public place, or your English pronunciation is not so good, that could be a really useful thing.
Other than that, I can't really see how Sara is any better... it is just a way of getting Siri like features to an iPhone older than a 4s.
It must be frustrating not to have features like Siri on your iPhone, but personally I don't like that the phone has to be jailbroken in order to install it.