I always prefer it over the RIVALS which u hav in mind.
WHY ???
In winter season the engine of SANTRO starts easily when their ENGINE REFUSE to START.
In summer season the AC of SANTRO makes the cooling when their AC REFUSE to make the cooling.
@huebleu
I think the problem actually lies here in ur case.
The
DRIVING STYLE of SANTRO
is a little bit different from the DRIVING STYLE of any CARBORATOR engine car. I mean the TIMING of the CLUTCH really does matter here.
I should give u my personal example.
When i was learning how to drive, I never made it in SANTRO and other car because of different timings of the CLUTCH.
What i observed for a new driver it is to some extend HARD to do driving in SANTRO.
But when u use to it u really love it then.
Also when i gave SANTRO for TEST DRIVE to my 5 friends who r expert drivers but not with EFi.
At first attempt
they all SHUT the ENGINE
exactly like a new driver. 
And after wards they didn't make to run the car PERFETLY aswell. Believe me 2 them then started making wrong comments about SANTRO at the same time just like it is underpowered or rubbish. But when i got the driving seat, they then realized that their comments were totally wrong.
It really effects on the milage and performance aswell.
And YES do u use to wash the engine of the car properly ???