I recommend you if you are looking for mileage dont go for honda activa 125. Instead of that you can go for honda activa 3G/4G.
Since honda activa also using metallic body so stability is good. Mileage is same for both 3G/4G.
My father using 8 years before still the engine is good. In my own experience I never seen such a low maintenance vehicle and running more than eight years with the same smoothness of engine performance.
Heavy person also can sit comfortably.
Disadvantage:(compare with Suzuki access)
1) We cant able to use for long drive.
2) Suspension is not present in this vehicle.
3)Height adjustment is not present.
4) Petrol valve present inside the seat.