(1) Restate has latencies that to the best of my knowledge are not achievable with Temporal. Restate's latencies are low because of (a) its event-log architecture and (b) the fact that Restate doesn't need to spawn tasks for activities, but calls RPC handlers.
(2) Restate works really well with FaaS. FaaS needs essentially a "push event" model, which is exactly what Restate does (push event, call handler). IIRC, Temporal has a worker model that pulls tasks, and a pull model is not great for FaaS. Restate + AWS Lambda is actually an amazing task queue that you can submit to super fast and that scales out its workers virtually infinitely automatically (Lambda).
(3) Restate is a self-contained single binary that you download and start and you are done. I think that is a vastly different experience from most systems out there, not just Temporal. Why do app developers love Redis so much, despite its debatable durability? I think it is the insanely lightweight manner they love, and this is what we want to replicate (with proper durability, though).
(4) Maybe most importantly, Restate does much more than workflows. You can use it for just workflows, but you can also implement services that communicate durably (exactly-one RPC), maintain state in an actor-style manner (via virtual objects), or ingest events from Kafka.
This is maybe not the first thing you build, but it shows you how far you can take this if you want: It is a full app with many services, workflows, digital twins, some connect to Kafka. https://github.com/restatedev/examples/tree/main/end-to-end-...
All execution and communication is async, durable, reliable. I think that kind of app would be very hard to build with Temporal, and if you build it, you'd probably be using some really weird quirks around signals, for example when building the state maintenance of the digital twin that don't make this something any other app developer would find really intuitive.