Wych drugs

Would somebody mind talking me through the math hammer behind the recommendation of +1 attack over +1 strength. Every time I try to calculate it for myself the +1 strength always comes out on top

I did wounds inflicted after saves by units of 10, only accounting for the Hekatarii Blades, not any Agonizer or Wych weapons. This also does not include the Hekatrix extra attack because it would have been a PITA to do in the spreadsheet.

Base Wych Attacks (S3, 3 attacks)
GEQ: 6.67
MEQ: 2.22
TEQ: 1.11

+1 A (S3, 4 attacks each)
GEQ: 8.89
MEQ: 2.96
TEQ: 1.48

+1 S (S4, 3 attacks each)
GEQ: 8.89
MEQ: 3.33
TEQ: 1.67

So yes, Strength is better against MEQ and TEQ, but equal against GEQ. Since you almost certainly have more than one Wych squad, take your +1 Attack drug unit towards a Toughness 3 target, and the +1 S to a tougher one.

I didn't do the math, but generally speaking, the more attacks will win out against anything with an Invulnerable save. I'd have to put custom T3 5++ and T4 5++ targets into the spreadsheet to get the numbers. If you really want them (if you play Chaos a lot) I can do it.

There's also a Mathhammer spreadsheet somewhere in the general forum.

Here is a hopefully simpler way to look at this.

Compared to a Wych with one of the other Drugs:

+1 Attacks increases attacks from 3 to 4 so improves damage output by 33%

+1 Strength increases the wound rate, but at different amounts depending on toughness
vs T2 increases wound rate from 4/6 to 5/6 so improves damage output by 25%
vs T3 = +33%
vs T4 = +50%
vs T5 = 0
vs T6 = +100%
vs T7 = +100%
vs T8 = 0

Depending on the targets you match up against, strength will be better or the same against most infantry, but won't help out with Agonisers if you spent the extra points for those.

The types of save don't impact the relative value of Combat Drugs.

You can increase the complexity again by including the Obsessions as well, which can give another source of attacks or strength. Against most (but not all) targets, the best combination is Strife with strength drugs or Cursed Blade with attacks drugs.

Have a look at this.
Wich Wych is wychest?

That flail math is interesting, I was pretty convinced gauntlets were the way to go every time. Still, with a Succubus nearby the flail benefit mostly disappears, and you're trading re-roll wounds for an extra attack, with the former usually being more useful.

In the strength vs attacks argument, I think it is worth mentioning that strength matters a little less in 8th and that s3 is just as effective vs t5 as s4 is. However, that equality drops off against t6 targets and above, so when making the choice I think it's worth thinking about whether you'll be facing more t5 or 6.I'll admit though that's often not the optimal wych target, it's probably better to think about facing t4 vs t3.
That all being said, I'm liking wyches more and more these days and I've been starting to take 2 units of 10 pretty regularly, so one unit is pretty much always going to be the +1 A while the other will be +1 S.

I find it’s a slippery slope. You like the one S4 A4 unit, so you take another, then you may as well take a third, but a 5-strong squad is weak so you want a third unit of 10, but run out of ideal drugs, so you take a Red Grief Outrider to dump the extras so you can have 3 S4 A4 Wyches.

Eh I don't find it too slippery a slope. 2 units of 10 wyches basically gives you 2 full effectiveness wyches, and then for the third for a battalion I'll either take +1 toughness if I don't have many other cult units which isn't bad, or I'm running a couple small reaver/hellion units so I can have 1-2 duplicate drugs.