background: 6'3, 165 lbs. looking at getting some Line Prophet 90's; my only worry about a 186 is that it might be a bit long for tight trees (NH). everything else points 186 but i'm just wondering if it would be worth a little length to get a little more quickness.
I'm 6'1" and the same weight, I skied a 186 S3 last season. It took my like 2 days to get used to the length, but after that I was really happy with my size choice. Go for the 186, it may be slightly less maneuverable in the woods but you will make it work.
Even if they ski short that won't change if they can fit between trees as op wants.
It's really up to you OP, I personally may have gone with either, but it really depends on the trees and your skill level. 5cm of ski length won't make a difference as long as you are actually skiing the trees and not sideslipping parallel to the slope.
I claim no responsibility for whatever retarded shit I just said up there
Another vote for the 186. As said line's measure up shorter and at your height and weight and from how you speak about skiing you should be able to handle them fine. Although its a diff ski i got 179 blends, loved them but kind of wish I had the 186.