I had the same dilema a couple of years ago. Moved from a Handjob (which I loved)to the Soul which is awesome and built it up with XT and 130mm Revs. Fantastic bike which I still love to ride.
I then had a demo at Dalby on a Zesty and like you, fell in love with FS (quite a good climber and a hoot on the downs). I bought one 6 weeks later, but ended up not swapping over any of the kit, but just upgraded when parts started to wear.
I have kept both and was really pleased in the end, as the Soul is just so iconic and carries alot of good memories of great rides. Having said that, the Zesty has also a few great tales to tell now its two years old.
Keep both and love them both for what they are.
Good luck