Food For Thought: Deploying First or Second
Like deployment, for me the choice to go first or second is influenced by a number of factors, primarily the mission, my army and my opponent's army (perhaps this is stating the obvious!). For Purge the Alien, Emperor's Will and Relic, I'm much more likely to choose to go first to attempt to get ahead on kill points, first blood, or grab the relic. Otherwise, the benefits of having the last word in multiple objective missions, linebreaker and being able to try to counter my opponent's deployment usually mean I will choose to go second.
If you're interested in reading more on the subject, I recommend this post by Kirby on 3++.