A: Ester formulations enter weeds more rapidly but also volatilize at warmer temperatures, which can burn the turf and harm non-target plants. In general, ester formulations are best used in early spring when temperatures are consistently cool.
Amine salt formulations are less volatile and typically used in landscape settings. Amines are better to use when temperatures are warmer and when drift to non-target plants is a concern.
As with all herbicides, always read the label for the proper rate, timing, and application instructions and to ensure that the product is registered for use in your state or county. The article Amines or Esters – Which Should You Use? from Penn State Extension provides a more detailed explanation of the topic.