Settlers are usually very marginal--you pick up Settlers when you have nothing better to do. But when the stars align, they can be great.
-You're keeping copper around
-You have +Buy or gain
-You are not drawing your deck
-Or, there are enough discard effects that you are discarding copper and not just estates/junk (any kind of discard works, including Warehouse, Ironmonger, and Cutpurse)
Bustling Village comes into play even less often than Settlers. As a strategy, Bustling Village has serious issues.
-It's a $5-cost village, which isn't a good price point.
-+3 Actions is good, but you'd really prefer the actions were spread out for reliability, like with Port or Fishing Village.
-It appears later in the game than you'd really want villages. It's hard to shift gears fast enough for it to be useful.
-The person who works hardest to reveal Bustling Village often stands to benefit the least from the village effect, because they've been wasting time on Settlers, a non-terminal card that is best in big decks. Sometimes by this point you've thinned your deck, but then the discard-to-hand effects aren't so good anymore.
-Putting settlers in your hand is great, if you can do it. But ultimately this is roughly a lab, and well maybe you could have just bought a lab instead. Bustling Village-Settler-Copper chains are rare even when the stars do align.
Tips for playing with Settlers/Bustling Village
-Consider going for +buy first. Settlers aren't so great in the first shuffle.
-Just because you have 5 settlers doesn't mean you want all the Bustling Villages. You want some nice terminals too, or else they're glorified labs.
-If your opponent got 5 settlers, only go for Bustling Villages if they're good for your own deck. Taking them away from your opponent usually isn't useful.
-Trigger that midturn shuffle! Settlers remove copper from your discard, making it a better shuffle to trigger. Furthermore, on cleanup all those settlers and coppers in play will go into the discard pile, which is exactly where you want them. Of course, this presumes that you have >5 cards left in your draw pile.
-If you have the choice of discarding junk vs copper, and can put the copper into hand, consider discarding the copper, as it improves the midturn shuffle.