Magic_Umbreon
Researching Tower Scientist, Retired
If an Ultra Ball is 2, a Dusk Ball (when used properly) is 3.
EDIT: If you can get a pokemon into the red and alseep in less than five turns a timer ball is by far your best option; if an Ultra ball is 2 (with a pokeball being 1), then a Timer Ball when used in the first five turns is a 4.
Dusk ball is also 4. The number represents part of a formula, not necessarily directly proportional to chance of catching.