Ok, so one thing people won't talk about is temperature vs battery use. If you're out in the cold and the battery pack is on your head, you will burn through batteries QUICKLY
So, for me, having a torch with a battery pack I can store close to my body to keep it warm is non negotiable.
I own two, a Black Diamond Ikon 700 which has many many settings and options for batteries, it is weather proof and the AA batteries last nights not hours when managed properly
I then also have a Silva Trail Runner Free which has numerous battery options as well. It is lighter and smaller and very comfortable, but not as hardy as the BD Ikon.
A headtorch for me is not something i feel I want to 'get away with using', so I am happy to spend money on it.