Marcus Orealias shot me an email essentially asking me to talk about my experience using the DF16 camping rules.
Let's talk my experience, and then ways to make all three choices worth considering each and every time you make the roll.
I love the camping rules in DF16. The roll + choice combination made for some interesting debates.
In my experience, my players always took Comfort plus one additional. They may have taken Concealment and LoS when concerned about a patrolling dragon, but I don't recall.
Comfort wins out for them because the loss of FP for lack of a comfortable campsite is steep. Losing 1 FP for the day - not recoverable except in town or by spending a night in a comfortable camp - really hurts the spellcasters. Throw in extra losses if they lack gear, if the weather slams down, or the GM is just being mean about the conditions, and spellcasters can be seriously weakened. It doesn't help Chi skill dependent Martial Artists any, either.
The tossup was always between concealment and lines of sight. This was an interesting choice.
Lines of Sight gives a bonus to spotting foes approaching the camp, and it was critical to allow the PCs to spot incoming creepy-crawlies, identify sneaky goblinkin, and otherwise ensure they made their Per rolls and weren't surprised. That often allowed the party to break out ranged weapons and spells and keep things off of them. Against very high Stealth creatures, the bonus to Per can make or break you.
Concealment, on the other hand, gives your opponents a hard time to find you (assuming your Camouflage is up to standards.) On top of that, it potentially gives you a second roll to spot incoming foes - again, if Camouflage is high enough. Hide well and you get two chances.
Ideally you have all three, which is what Serendipity and critical successes are for.
Making the choices tough
Drive home the importance of Lines of Sight with foes who sneak well. Make it so that the +1 to Per and the -1 to Stealth is potentially the margin between spotting a foe and being awake and ready or have an obsidian tiger or ooze or troll jumping you from behind while the rest of the party sleeps. Also, make it clear that choose Lines of Sight can mean good Lines of Fire, too, and that you may spot foes far enough away to engage them with ranged weapons and spells. Scouts generally prefer this to "you'll wake up just in time for melee!" since their skills make range valuable to them and a hindrance to foes.
Challenge Lines of Sight with foes that sneak very, very well. Also, challenge it with foes for whom spotting isn't an issue - invisible foes, teleporting foes, or extremely fast foes. For those, Lines of Sight really don't matter very much.
Make Concealment useful by using foes who hunt by sight. Especially lethal foes - dragons, eyes of death, scouts for large armies of fodder or worthy foes, etc. - these make hiding well a critical issue. Although the rules don't specify this, it's quite possible that foes failing to spot you might just pass campers by.
Challenge Concealment with foes who hunt by senses other than sight. Detect Life (Precise), Discriminatory Smell, exceptional hearing, etc. work well for making Concealment a sub-optimal (or even useless) choice.
Make Comfort important by including encounters that push PCs to the FP limits, and strictly enforce the rules for recovering the FP lost, here. If you handwave it and say, "I let them rest 10 minutes and get it back" it's just not going to be worth taking. If it's as written, it's critical to seek comfort - and bring the appropriate shelters (DF16, p. 24)!
Challenge Comfort by making Lines of Sight and Concealment more important. It's foolish not to take comfort as a default, if only because of your spellcasters. But given foes that hunt by sight and are potentially seeking you out, it might be worth being down 1-2 FP the next day and getting +1 to Per and +1 to Camouflage and giving -1 to Stealth and -1 to Vision.
Given the right mix of potential foes - especially if you've been aggressively signalling what's out there (dragon sightings, rumors of trolls, signs of an orc army, slime trails from oozes, etc.) - the players have some real choices to make. By following the spirit of the rules - sometimes you'll hide well enough and they'll miss you, sometimes nothing comes and only comfort was worth having, sometimes LoS means you spot them far enough off to break camp and leave - you'll make it a fun choice, too.