Two adamantine mail shirts beats an adamantine robe any day, I would think.
Breatsplates provide a lot of defense, but leave the arms exposed.
Robes (and better,
dresses) cover the face. (and fingers?) Nothing else does. Note the
Armor entry in the wiki. The UB/LB step MAX is coverage of those areas regular armor just can't reach.
dresses have a smaller SIZE than robes, if it matters. It's hard to figure out this release, the permit numbers aren't always work how you'd expect, but my testing in adventure mode had
two dresses under 2xMail shirts, where only one robe would fit. I don't know if Fort dwarves can equip two dresses at once (or two mail shirts, for that matter).
Note the superiority of Chausses (only foot protection to go up the leg) and Long Skirts (LBSTEP:MAX) as well. Both of which you probably can't make. Unfortunately. You can (in adventure mode, again YMMV for fort mode) layer WAY more long skirts in than trousers.
Perfect world scenario (if layering is allowed)?
a
helmet under as many
hoods as possible.
2
dresses under 2
mail shirts*, as many
cloaks as can fit
multiple long skirts (Can't be blue I don't think dwarves can make them) under
greaves (maybe also a loincloth, but if you're wearing a kilt...)
chausses (definitely not blue, probably traded-for rope reed) under
High Boots gloves, under
Gauntlets.
* breastplates may be better, if you've got the
dresses, since breatplates have an armor rating of 3 vs. 2 for mail shirts, but I have yet to get an explanation on what that
does; aou can layer mail shirts with and they have UB & LBSTEPs of 1 vs. Breatplates utter lack of coverage of arms.