I made a simple calculator that shows how Wigglytuff is the 9th-fastest and the 5th-most revive-efficient prestiger against Ditto.
– We are going for 1000 prestige, so we need to attack a level-N Ditto with a level-N/2 Pokémon.
– No attacker switching after Ditto’s transformation.
– Ditto copies the attacker’s moveset, Attack and Defense stats, but keeps its Stamina stat. However its new CP is calculated from the attacker’s stats, including Stamina.
– Everyone has 7.5 IVs for all stats. Even better results are obtained with a 15/0/0 Ditto, because Ditto keeps its IVs.
– In the “Simple” sheet, type effectiveness and moveset DPS(1) are taken into account. In the “Super Simple” sheet, the rank is just done by Att x Sta / Def.
– The fastest prestigers, due to their high Att/Def ratio, are Gastly and Haunter , but their low Stamina makes Ditto useless (just fight Gastly with another Gastly, it’s much more efficient).
– The most revive-efficient prestigers, due to their high Stamina (which gets replaced by Ditto’s Stamina) are Blissey , Chansey and Snorlax , but they are slow due to their low Att/Def ratio.
– Wigglytuff has an Att/Def ratio of 1.7, so it beats itself quite quickly, but it has almost 3x Ditto’s Stamina, so Wigglyditto will faint very soon.
Pound is a must-have, because it’s neutral (not NVE) and fast, so Wigglytuff can use it much more often than Wigglyditto.
– Pound / Hyper Beam: recommended against high-level Ditto. According to Pokébattler, the first, deadly Hyper Beam can be fired with 88 seconds on the clock, before Wigglyditto can use its own.
– Pound / Dazzling Gleam: Not suitable against a level-30 Ditto, but a level-13 Wigglytuff with £/DG can defeat a level-26 Wigglyditto with 7 Pounds, 1 Dazzling Gleam and 5 more Pounds.
– Pound / Play Rough: it should work starting from level 12 vs. 24 (after 7 Pounds, 1 Play Rough, and 5 more Pounds, a level 24 Wigglyditto should faint).
(1) For the best moveset per species, the source is my Choose Your Prestigers v8.0. For type effectiveness, I just typed my estimated values manually.