Underquilt on the inside / sock on the outside has more advantages, namely the extra windbreak layer that should stop drafts between you and the underquilt, ease of adjustment from inside the hammock, being able to pull the sock back when you need to go for a piss in the middle of the night and not have to readjust the underquilt... Can't really see what advantage there would be the other way round though. 

I have the Dutchware vented summer sock that I plan on 75% of the time this year (tons of mosquitoes) 

I am currently underquilt shopping, and my question is, will I want the underquilt on the outside, or inside of the sock? 

Underquilt with bug sock