If you are staying at AKL, I'd do both on a resort day. Relax somewhere quiet in the morning, make an 11:30 Sanaa ADR for lunch (it's the earliest they open and you will have no problems getting a window table), head back and sit by the pool for a few hours, nap, shower, pre-dinner drink at Victoria Falls, dinner at Boma sometime around 7:30-8.
AKL has the 3 best restaurants on property, IMO. Sanaa is the best TS (usually our go to for lunch on a pool day at AKL), Boma is the best buffet and Jiko is the best Signature. Between Sanaa and Boma, if I really had to choose only 1 (when staying at AKL, we make it a point to get to all 3), I would probably choose Sanaa purely for the bread service.