It depends on many factors. For clean compile, ksp...

# room

[yigit]

It depends on many factors.
For clean compile, ksp was significantly faster.
For incremental, it was usually faster but there were also cases where kapt 's incremental works better than KSP.
One such case i recall was multiple classes in a single file.
KSP does invalidations based on files vs kapt does based on classes generated from those files.
I recall the Gradle profiler scenerio implementation was doing a non abi change on a KT file by adding a line, which was no op for kapt but was invalidating KSP.

TL;Dr; it depends. But in theory, KSP has a better theoretical speed limit compared to kapt due to lack of stubs step.