Lowest scenes taking more time than heaviest scenes.

Hello, This is making me nervous, because it makes no sense to me.
I did a test with decimator
Scene number 1
Resolution (polygons): 607.068
Materials memory consumption 417.371 KIB (GPU)
Two genesis 3
clothes and environment with textures with 2048x2048.
Photoreal (Fullhd), i only change in progressive rendering, max samples to 2000, max time(secs) to 20000 and rendering quality enable (off)
this scene take 1 hour, it's ok for my computer!
Scene numer 2
Resolution (polygons): 321.643
Materials memory consumption 255.195 KIB (GPU)
One genesis 3
clothes and environment with textures with 2048x2048.
Photoreal (Fullhd), i only change in progressive rendering, max samples to 2000, max time(secs) to 20000 and rendering quality enable (off) same thing.
this scene take 2 hours and a half sometimes 3, and sometimes sends the process to CPU, then render time takes 6 hours, probably something like that.
Is it a bug, or is it just something I don't understand? please someone explain to me... and hope you guys understand my english.
Comments
Hello, This is making me nervous, because it makes no sense to me.
I did a test with decimator
Scene number 1
Resolution (polygons): 607.068
Materials memory consumption 417.371 KIB (GPU)
Two genesis 3
clothes and environment with textures with 2048x2048.
Photoreal (Fullhd), i only change in progressive rendering, max samples to 2000, max time(secs) to 20000 and rendering quality enable (off)
this scene take 1 hour, it's ok for my computer!
Scene numer 2
Resolution (polygons): 321.643
Materials memory consumption 255.195 KIB (GPU)
One genesis 3
clothes and environment with textures with 2048x2048.
Photoreal (Fullhd), i only change in progressive rendering, max samples to 2000, max time(secs) to 20000 and rendering quality enable (off) same thing.
this scene take 2 hours and a half sometimes 3, and sometimes sends the process to CPU, then render time takes 6 hours, probably something like that.
Is it a bug, or is it just something that i don't understand? please someone explain to me... and hope you guys understand my english.
Sounds a little like SubD is turned up high for a figure or clothing or hair in the second scene. Just guessing.
What packs are in the scene that you are trying to decimate?