There are two identical meshes.
The only difference is in units. 1 - in mm, 2 - in cm.
I changed the size of the mesh in the slow file and it still remained slow.
1 - sculpts quickly, 2 - sculpts slowly.
Two windows of the same blender version are open. 1 - file is fast, 2 - file is slow.
I found a pattern. If the file is exported from 2.7 it is sculpted slowly. Obj, colada, fbx - give a slow result. So far, the solution for me is to export to gltf. If you do export to gltf from 2.7 to 2.8 then to 2.8 sculpt quickly. Perhaps this is a temporary problem in the new build 2.8 that I downloaded today.
There were no problems in the previous build.