The GPU of Strix Halo is many times faster than the GPU of the biggest Orin AGX.
The Strix Halo has 25% more "CUDA cores" (2560 vs. 2048), which work at a clock frequency that is more than double (2.9 GHz vs. 1.3 GHz) and which can have for some operations a double throughput even at the same clock frequency. The memory throughput is also higher by 25%.
The GPU of DGX Spark will have to be 4 or 5 times faster than Orin to match Strix Halo as a GPU. This is not at all certain because NVIDIA has stressed only AI/ML applications without saying anything about graphics.