ΔE 6.9, close: similar, with a visible difference side by side. Light Gull Gray is a little darker than Medium Sea Gray (RAF).
Usually, if you are not matching paint already on the model. Close match (ΔE 7). Light Gull Gray is a little darker than Medium Sea Gray (RAF).
The same difference applies the other way round: Medium Sea Gray (RAF) is a little lighter.
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 Medium Sea Gray (RAF) on the colour wheel See Light Gull Gray on the colour wheel
All matches: Medium Sea Gray (RAF) equivalents · Light Gull Gray equivalents