We'll have to wait until we see more deeper results and analysis after the M3 Ultra and M4 Max come out next week in the Mac Studio. But here's where i think the difference will be significant in terms of performance.
The GPU in M4 Max brings Apple’s advanced graphics architecture (second-generation) to Macs, including dynamic caching, hardware-accelerated mesh shading, and [most importantly] a second-generation ray-tracing engine for more seamless content creation and gaming. As Apple notes in its PR, "Mac Studio with M4 Max starts at 36GB of unified memory, with support for up to 128GB, so users can do everything from sorting through thousands of images with speed and precision, to producing complex compositions with hundreds of tracks, plug-ins, and virtual instruments, all played in real time."
However, the M3 Ultra with Apple's advanced graphics architecture also brings Dynamic Caching, along with hardware-accelerated mesh shading and ray tracing [first generation/2x slower ray-tracing engine], so graphics workflows like GPU-based renderers are up to 2.6x faster than Mac Studio with M1 Ultra.
Key point is that the CPUs across the M4 family feature the world’s fastest CPU core, delivering the industry’s best single-threaded performance, and dramatically faster multithreaded performance. The GPUs build on the breakthrough graphics architecture introduced in the previous generation (M3), with faster cores and a 2x faster ray-tracing engine.
In conclusion, if you want best ray-tracing performance, the M4 Max GPU builds on the breakthrough architecture of the previous generation (M3), with faster cores and a 2x faster ray-tracing engine.