Hello romullus,
--- CORONA SKY (v5.0) ---I used the old v5.0 Sky & Sun, since I wanted to compare v5 and v6.
I did a lot of test this morning with v6.0 and:
(*) PT and UHD give me the same exact result (except for the noise, obviously).
(*) 4K is very different (as lighting) from PT and UHD Cache.
(*) 4K produces strange noise under the balcony.
(*) 4K is very slow!
--- HDRI VERSION ---I also tried CoronaSky + CoronaSun vs HDRI.
Here you see the HDRI version:
(*) PT and UHD give me the same exact result (except for the noise, obviously).
(*) 4K is very different (as lighting) from PT and UHD Cache.
(*) 4K doesn't produce any strange noise and the fireflies are much less (good).
(*) 4K is very slow!
So, I think that something is wrong in the 4K Cache + CoronaSky/Sun