3 D6 pick 2 vs 2 D6 with 1 reroll I was wondering if there is any statistical difference between rolling three 6 sided dice and taking the best two (looking for a 7 or higher) and rolling two 6 sided dice with the option to re-roll one?
 A: If the goal is to obtain 7+ eyes and there is no preference about the total score otherwise - then there is no difference between rolling 3 vs rolling 2 and re-rolling the lower one when their sum is lower than 7.
Think about it like this:
You roll 3 dice. You look at the first 2 of them. If they do not sum to 7 you look at the 3rd. But you will always want to add the 3rd to the bigger score of the first 2. There is no sense in keeping the smaller one.
This exact scenario plays out with 2 dice, except instead of discarding the lower of the two and looking at third - you re-roll the second die.

However if the total score matters and i.e. 9 is better than 8 then there is a difference. In this case as another answer pointed out - when you re-roll the second die you might actually get a lower number than it had before.
A: Absolutely there is a difference between the two. In the first case, you are guaranteed to roll three dice and ignore the lowest value. In the second case, you can roll three dice, but it's possible that you get stuck with the lowest value on your last roll. This die would have been ignored had you rolled all three simultaneously, as in the first case.
"Roll three-pick two" will on average yield a higher total than "roll two-reroll one". If you assume the same sequence of dice rolls tested for both strategies, "roll three-pick two" will always yield the higher total.
