For Disney -
I do the advance research.
I present a short list of hotels to DH and DS and we decide together.
DH books the hotel, as well as the flights and rental car, if needed.
The guys give me their "must do" and "hope to" choices for each park, and I do the detail planning/ADRs.
For other trips, DH usually researches the hotels, and I research the activities.
Date nights could be either of us, are more likely planned by DH than me.