I had an environment that was using a couple of materials with 47 UDIM tile textures loaded in CoronaBitmap loaders piped into a 'MultiTIle' node, and I was experiencing slow render times compared to when I split out the single material into 47 separate materials not using any textures as UDIM tiles. I measured the render times to be 200% - 300% slower using textures as UDIM tiles.
The reason using UDIM tiles are preferable is because they are automatically and easily output by 3D painting apps. Also, obviously, because it's a lot easier maintaining a few materials than 47 of them.
