DGX Spark is at the compute level of 5070. Its main issue is low memory bandwidth, i.e. it has quite fast token prefill but awful token generation. Strix Halo is just slow on every metric and used to be a cheap way to get 128GB unified RAM (now its prices are comparable to DGX Spark).
I have one, this isn't true. The wattage of a 5070 is about 300. The spark entire unit runs at 200 watts max. In reality it runs like a rtx 5060 with lots of vram. Very good for training, okay for inferencing if you are running batch jobs and don't mind waiting.