One thing I've found about 12 string sets of strings is that if you bend your strings the octaves stay in pitch together, I replaced a high G with probably a 10 when it broke and when bending the two strings went horribly out of tune with one another.
I now mostly have standard G strings, not as authentic but I like the sound and it's more practicle, also that way go up to the top end of the neck and you can get some good Ronnie Wood mandolin sounds Maggie May etc.
Geoff M