Only point lights affect indirect lighting on RTGI much less than other types of lights.
Indirect lighting of baked lightmaps look much stronger than RTGI.
Apparently, it's because only point lights are divided by 4*PI in SetupLightParameters of Engine\Source\Runtime\Renderer\Private\RayTracing\RayTracingGlobalIllumination.cpp
I removed the 4*PI then it fixed this issue and indirect lighting from a point light on RTGI looks more similar to baked lighting. (Shelved CL: 14023328 on 4.25plus)
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-96362 in the post.