The head was larger, allowing better light transmission, so my understanding is that it was used in lower light conditions, bright nights and maybe a darker dawn/dusk, but not on a dark night. The attack scope was only used during the day, and by some accounts during brighter dawn/dusk.
What’s interesting is that in most newsreels you see attacks happening from the observation scope, particularly Topp, but I think that goes to Fifi’s point, the lack of space in the tower for filming, as well as confidentiality. The Standsehrohr attack scope was a phenomenal piece of equipment. I have seen footage of the skippers turning around on the attack scope, but not very often.
As far as the optics and reticles are concerned, substantially the same as the attack scope.
Good detail here:
http://tvre.org/en/aiming-with-the-periscope