My last post talked about Gloomhaven and how to compare various potion effects. Ferris commented that he hugely valued the extra turn a stamina potion can give, and he felt like just that effect alone was more effective than a healing potion for 3 health. This made me think a lot about card efficiency so I am going to ramble a bunch about that. The potions I was referencing look like this:
For this post I am going to just talk about low level content with the starting classes and equipment; the conclusions change dramatically at higher level.
There are multiple ways to get extra tempo in GH by losing cards. The simplest is just pitching a card to avoid damage. In the early going this is probably saving you about 4 damage. It is fantastic for tempo as it does not require you to spend an action to do it, and that tempo is worth a full top action. It also usually costs you about 3.5 turns of longevity. It *could* cost you five turns if you do it at the outset of the game or as little as 1 turn at the end, but I am going to average to 3 here, assuming that you pitch that card when your next hand size would be 6 or 7. That extra .5 of a turn is the penalty of losing an extra card from your hand, which shrinks your current number of turns by 0 or 1.
A lost card gives a bigger effect than a card pitch. For example, the Brute has a solid Level 1 loss that saves 6 damage. However, you have to actually play the card, so while it is better than a card pitch in power it loses you the ability to play another action. This, if you accept the model above, is a loss of 3 turns in longevity for an effect that is about twice as good as a normal play. Loss cards that grant attacks can't be as easily compared to pitching a card, but there is a model of card efficiency that can help us. Lost cards are usually twice as good as used cards, whether they are defensive or offensive.
Keep in mind that AOE damage isn't as good as single target. Sure, the Spellweaver can Fire Orbs to hit 3 targets for 3, but that isn't three times as good as a default Attack 3 Range 3 effect. If it were 3 sequential Attack 3 Range 3 effects it would be, but it isn't, so it actually fits the model of being twice as good pretty well.
Lost effects and pitching cards gets us the effectiveness of an extra action right now, but costs us 3-3.5 turns at the end of the game. Clearly you do this when you have to, but you pay a high total output price to gain that spike of power.
Now I can use these standards to compare potions again. If you are in a scenario where you never need to use lost effects or pitch cards to reduce damage then the scenario is trivial and nothing matters. Keep in mind for this assumption, we are talking about low level here. Sure, your level 9 party can lock down all the enemies so none of them get to swing and pitching cards won't matter, but at low levels you simply cannot do that and getting beat to death is a constant risk presuming you are playing at a difficulty that is a challenge for you.
Assuming that you need to use lost/pitch effects to survive, a stamina potion grants you 1 extra turn. If you can use a healing potion to avoid pitching or losing a single card, you save yourself 3-3.5 turns. A healing potion adds roughly the same level of tempo that a lost card or a pitched card does, so this is a reasonable comparison at low level. You can sometimes do better than that if you happen to pitch to avoid a big 6 damage critical hit, but even then the healing potion is far superior than the stamina potion in terms of efficiency - on average, at least. At the beginning of the game a healing potion is even better because it can give you more than 3 turns, at right at the end of the game you are on your way out anyway so a healing potion can be as little as a single turn.
Of course the stamina potion lets you reuse specific cards, and gives you flexibility in rest timing. Those things are real. Still, I think if you want pure longevity you are actually better off with a healing potion to get you through rough patches rather than a stamina potion because you can avoid losing or pitching cards with that healing for backup. Certainly a Cragheart or Brute, who has a large health pool, can make better use of a healing potion. They also have weak combo potential, so the stamina potion is not that exciting at the outset. A flimsy character like the Mindthief though struggles with a health pool of size 6, so they often can't even use the whole healing potion but still are worried about dying.
Some of this holds true as you level up. High level loss cards and card pitches scale up in power but have the same cost in longevity. Low level loss cards become worthless though as the effect is not worth the cost in time. There is no point in losing a card to heal for 6 when a normal monster swings for 6!
However, stamina potions scale effectively while healing potions do not. At higher levels stamina potions let you reuse powerful high level effects giving you a huge tempo boost as well as improving flexibility, rest timing, and longevity. Healing potions, on the other hand, fade into obscurity. Better than nothing, sure... but vastly inferior to stamina. At the beginning there is a real argument to be made for each of the starting potions depending on your class. At the end though, the conclusion is simple - stamina > all.