Why not let him flip the coin himself. The difference will not be that great.
I have a pair of 210 cm GS Comp straight skis in the basement that are waiting for a deserving mantelpiece. It was once the gospel to get the longest ski you could 'handle'. My gospel now is to get the shortest one that will still do what I want. I am also 180-190 (depending), and my favorite skis are Volkl Explosiv CMH edition in 165. I bought them that length so they'd be lighter for skinning, fully expecting to give up a bit of performance. They turned out to be the most powerful all mountain ski I've ever owned. Individual preferences vary of course and it is hard to buy a bad ski nowadays.