I can't tell which is the best stat for farming the wasteland though. What has everyone else found?
At this order: Endurance, Strength, Luck.
If your endurance is higher then 10, you're completely immune to radiation.
Luck = caps
strength = more damage to enemy = less damage from enemy = longer exploration = better equipment
High strength means you can carry more stuff. Your explorer will turn around and head back home by himself if he reaches his carrying capacity, so you want him to be able to carry more stuff and stay out longer so he'll find better stuff.
Luck = caps.
High endurance means you live longer.
I like the Movie Fan Outfit. It's pretty good, at at +4 Endurance, your dweller won't replace it if he finds a +3 Comedian outfit of something. Sturdy Wasteland Gear is +5 Endurance, and it's fantastic.
The higher your endurance, the more healthpoints you'll get. Send them out with the highest endurance you can, always, so that you wind up with a high level dweller with high healthpoints instead of wimpy points.
But none of the stats actually go higher than 10, do they?
They don't, but the bonuses take it over 10. i.e. you can be 10 for strength, but put on some +5 Strength clothes and the dweller is effectively 15 strength (10 + 5)
Max SPECIAL first or at least the E, if the character you are sending out is less than level 50, send them out in your highest endurance clothing that won't change, so Sturdy Wasteland Gear should be the minimum. This is because your health point max will be much higher. As you level, you get bonus health points based on the level of your endurance, and clothing counts as that bonus.
After level 50 with maxed special? First I use my best clothing items that have at least 1 E so they don't sustain radiation damage, such as Bittercup's outfit, and Autumn's outfit. If I've run out of legendary outfits that have at least 1 E point, then I put all the men in the Wrestlers outfit 2 S, 2E, 1 L and all the women in the Soldiers Uniform which has the same stats.