ΔE 17.3, loose: different enough that you should pick on purpose. Ethereal Green is noticeably darker, much more saturated than Nurgling Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Ethereal Green is noticeably darker, much more saturated than Nurgling Green.
The same difference applies the other way round: Nurgling Green is noticeably lighter, much more muted.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See Nurgling Green on the colour wheel See Ethereal Green on the colour wheel
All matches: Nurgling Green equivalents · Ethereal Green equivalents