Avraham and Tzo'ar

The story of Sdom has always been an interesting one. Today something hit me while reading the parsha:

Avraham davens to Hashem to save Sdom and its 4 neighbors. After successively smaller numbers of righteous individuals can't be found, Avraham goes back home. He wakes up the next morning and the entire area has been destroyed. Why he stopped when he did, whether his davening was for each city or all 5 as a whole, see the meforshim there.

Lot, on the other hand, is told to leave because the city is about to be destroyed. He asks that Tzo'ar be saved, so that he can take refuge there, saying "their measure [of sin] is not full." Meaning they either weren't bad, or the city was inhabited more recently. Either way, Tzo'ar is saved.

Avraham davens, nothing happens. Lot asks and the city/village is saved. Interesting, no? The pleas have different perspectives too, Avraham is worried about whether there are tzadikim (either for them or because that means the city isn't irredeemable). Lot asks because he needs a place to go temporarily, before leaving.