Outlast is one of my favorite Scenarios. The rules for it are easy to understand, no killbox means no "gotcha" moments for newer players, and it scales really well in terms of complexity as terrain and opponent armies get added into the mix.
I would say that going first is slightly worse in general on this Scenario. The possibility of scoring 2-3 points and the importance of terrain makes it much more likely for me to take second on this one with many casters and lists.
The exceptions to this rule are the really fast, pathfinder heavy armies such as Legion, Circle, some Cygnar builds, etc. that can mitigate the terrain and like to dictate the placement of their opponents' armies. They will likely want to go first.
Game Plan for Going First:
Your job is to make venturing into those zones an unpleasant thought for your opponent, and to make it really, really hard for them to score in both.
Take advantage of any terrain inside the zones themselves to keep your models safe from a turn 2 murder spree. Sometimes just parking a heavy behind a wall is enough to ensure your opponent isn't able to clear that zone for a few turns.
Turn 1 you need to respond to how your opponent deployed. Some boards will lend themselves incredibly well to a second player skew on deployment, with 90% of their army obviously gunning for one zone.
You have a couple of options:
Send some hard to take out models like Daughters or Bloodrunners (both have Stealth, high speed, and high defense) to that side of the table and just play the contest game. They're going to have to start contesting the other zone sooner rather than later, and you can start killing their models with ease.
Counterswing your army so that you have an all out brawl in one zone, with a few smaller level engagements in the other. I only recommend this approach if your army outthreats their army by a significant margin or if you can use terrain to blunt their attack lanes.
If they deploy centrally, note where their heavies and Warcaster/Warlock are. That will broadcast to you which direction they are likely to swing. You need to make it difficult for their Warlock/Warcaster to be in that zone safely if at all possible. The threat of 2-3 high POW boostable guns is often enough for a Warcaster to skirt their range, and it may give Warlocks pause as well.
Turn 2, if you can already get some charges off with chaff models, go for it. Set the line of engagement right on their half of the table and prepare for a counterpunch. Baiting out a high value heavy with one of your own of lesser value also has some merit. The edges of the zones will be the important places in this Scenario, with the center devolving into a kill zone. Whoever can hold their pieces back for longer typically wins this fight.
Game Plan for Going Second:
You're planning on playing for Scenario if you chose to go second, and that probably means there are a couple of awesome terrain pieces that will prevent your opponent from significantly contesting one of the zones. A good example of this:
See the big forest on his side of the left zone? That's awesome for me, since I can reliably expect all of his contesting models to either be extremely slow coming through the forest, coming through the middle of the table where I can kill them off, or around the far side of the forest, which is a position that will leave them without support.
Turn 1, get your pieces in position for a turn 2 clearing of a zone and a control or dominate of at least one. This means that you need to think about where your opponent is likely to put his models the next turn. If he's got a forest to hide behind, you need to get your models to a point where they can walk or trample through the forest to shoot/hit his models.
If there's a big piece of rough terrain, expect your opponent to go around the edges of it and prepare accordingly with models in place to murder whatever comes that way.
Turn 2, hopefully what you expected to happen on your opponents' second turn has happened and you're in position to capitalize on his placement and score some points. You need to be prepared for an assassination run from your opponent if you start winning on Scenario, as this is usually their only option. Do your very best to deny them that angle.
Clear zone, get point, rinse and repeat. This is obviously highly list and terrain dependent, but it's a general game plan that has served me well in the past.