Ski Trip + Sightseeing. Should we buy a pass?

Hello,
I need help deciding whether it is worth buying a pass and if so, which one!
We are in Japan for around 19 days, below is a rough itinerary:
- Fly into Narita - Tokyo for a day - Train to Hakuba. Where we are skiing and won't travel for 6 full days - Travel to Osaka. Where we plan to do day trips to Kyoto, Hiroshima and Nara - Tokyo for the last 4 days (local travel only) - Fly out from Haneda

Is getting the JR Rail worth it? Or am I better off just booking the tickets separately? If a JR Rail is worth it, should we get a 21 day pass to cover the trip from the airport to Tokyo and then the train to Hakuba at the start of the trip? Or get a 14 day pass to start when we leave Hakuba for the end half of the trip?

Thank you very much for your help, it will be very much appreciated!