With Andy and Treachery an Ethereal Thresher averages 20 more damage per a sec than an Ethereal Mancatcher, and 70 more dps when using Jab.
However the Ethereal Mancatcher is 1 frame faster on both normal attacks and Jab. So arguably Crushing Blow will trigger faster and that’s probably enough to make the Mancatcher superior.
The Ethereal Giant Thresher has the same attack speed as a Thresher, so it’s always superior to a Thresher since it does more damage and triggers CB at the same rate. However it has significantly higher strength requirements, so maybe the slight increase in average damage is not worth it.
The Ethereal Cryptic Axe is both slower and does less damage per a second than the Ethereal Giant Poleaxe so it seems that no matter what you favor the Giant Poleaxe is always superior to the Cryptic Axe.
The Ethereal Giant Poleaxe is slower than the Ethereal Giant Thresher (1 frame slower on normal attack, but the same on Jab) but does more damage per a second, and it has lower requirements than the Giant Thresher.
TLDR:
Mancatcher is the fastest base, while Giant Poleaxe has the most damage per a second. If you care more about applying Crushing Blow the Mancatcher is probably better, if care more about damage per a sec Giant Poleaxe is.
Of course this is assuming Treachery and Andariel’s Visage without using an IAS jewel. If you add more IAS things can start to change again, but I think that setup is so expensive people who have it can figure it out themselves.
For completion sake I also looked at the other possible bases when using Andy and Treachery.
An Ethereal Stygian Pike has the same average damage per a second and the same frame rates as an Ethereal Giant Poleaxe while having lower strength requirements, so it’s an equivalent base, and slightly preferable to the GPA.
An Ethereal Ghost Spear has the same average damage per a second and the same frame rates as an Ethereal Giant Poleaxe and Ethereal Stygian Pike while having lower strength requirements but higher dexterity requirements than either, so it’s an equivalent base, but worse than both alternatives on the requirements front.
An Ethereal War Pike has significantly lower frame rates than any of the other choices, and slightly worse damage than a Giant Poleaxe, so not worth using.
TLDR after looking at all the options:
Mancatcher is the fastest base, while Giant Poleaxe or Stygian Pike has the most damage per a second. If you care more about applying Crushing Blow the Mancatcher is probably better, if care more about damage per a sec Stygian Pike is best, (slightly better than the GPA because it has a lower strength requirement).
However, all the bases with the exception of the War Pike (far too slow) and Colossal Voulge (low damage and slow) are close enough that it probably doesn’t matter to most players who aren’t trying to optimize an extra hundred damage per a second.