I don't buy armor because the stuff in boxes works fine. Unlike weapons, armor is generic (although divided into heavy, medium, and light) so I don't feel like using my precious resources on it because it doesn't unlock better specialties. I have bought armor once, but then it turned out that only Mokou could equip it. Despite the fundamental genericness, crafted armor is
unique to each character. They probably have cool effects too, that I'm completely ignoring. The wiki's armor section is completely blank.
Now that I'm motivated, I'm gonna translate the Japanese wiki and say what everyone's special armor does. The values of the bonuses go up with armor level, so resistances become immunities and percentage bonuses increase.
Reimu: Light resistance, extra bombs, extra lives
Marisa: Silence resistance, extra bombs
Sanae: Death/Removal from battle resistance, extra bombs, extra lives
Aya: Stun resistance, extra bombs
Sakuya: Consecutive hit chance up, bombs + lives
Patchouli: Magic reflect chance (?!), bombs
Nitori: Blind resistance, Perfect Dodge chance, Chaser power up
Alice: Paralyze resistance, bombs + lives
Satori: Confusion resist, Induction up, bombs
Youmu: Physical strikeback (?), counter chance, bombs
Mokou: Bless damage reduction (?), bombs + lives
Byakuren: Petrify resist, magic wall (?), bombs
Some of them are pretty boring, but a lot of them seem to be introducing new mechanics entirely. Maybe I should be paying attention to armor... Gonna look at shields next, just in case.