3-2 is better, check out drop rates here https://penguin-stats.io/result/item
This doesn't incorporate if farming a lower-rarity item and then upgrading via workshop is better, correct? I think for a lot of items it's better to farm lower-rarity than the actual item... Someone else had posted a link on that before but I can't find it now.
e.g. 1 Sugar Pack ~45 sanity per item if grinding the best stage for it (4-2)
required to craft is 4 Sugar, which is <40 sanity if grinding the best stage for that, S3-1