I Cannot speak for the automatic one. Will leave it to other users. I own a manual one.
If you live somewhere, where the roads are smooth and there is moderate traffic on it then Picanto is a really good option for you.
But if you live some place where there is bumper to bumper traffic, alot of Speed bumps or potholes than stick with Alto.
Manual Picanto if driven constantly at 100 km/hr on motorway will give you 20 liters per liter average with or without ac. And if you drive it at 120 km 16 to 17.5 km is the max, i was able to achieve.
Why 100 km, what ever is the half speed of your speedo meter, is where your car will run the most efficient, plus you are not overloading it.
Picanto is less aerodynamic that Cultus. From my experience it does not like 120km, feels like there is too much drag on it.
In city with AC it give me 13.5 liter per kilometer and without ac it gives me 15 liter per kilometer (I use Hi-octane, why higher octane is recommended in the manual,
On Islamabad highway it give me same 19 liter per kilometer average.
In bumper to bumper traffic, it will consume alot of fuel. Reason for bad economy in bumper to bumper traffic is kerb weight, its 100+ kg heavier than Wagon R, Cultus and Alto.
Power-wise its okay. Not a big fan of 2nd gear, its a bit sluggish if you try to pick the car when the air-conditioner is running. I came from 1500cc to 1000cc that could also be the reason why i feel this way.
Without ac power wise its on par with Cultus.
Ac performance is top-notch, you can compare it to 1500cc car.
Rear Leg room is ample, if you adjust your seat as per recommendation that you hands extend in front of the steeringwheel and your back and thighs are straight.
My advise would be to visit Kia dealership near you and test drive the car.