This is my friends first car. I own Santro 2007 model. By comparing both, this is almost similar to Santro but the difference below:
Driving is little more comfortable in i10, may be due to the engine. No noise audible inside, very soft.
The headlights are projected up a little, that makes it look like a mini lorry on the front side:).
I feel i10 is little short in hight when compare to Santro, but still this car suits me well(I am 6" tall) for the driver leg space.
Interior looks better in i10.
AC is very good(same as Santro).
It gives the miliage of 17+ in long drive and 13+ inside city(Bangalore) per liter(almost the same as Santro; a bit better miliage in the city). Note: If we travel with 3 or more persons, then the miliage reduces 1-2 km / lit.
Like Santro we can drive it in all the roads in any condition and you must be careful in some of the bumbs on the road. Bangalore roads are of the worst condition in India.
Lke Santro, the 2nd gear pick up is low when AC is on. When you switch off the AC, you can see the dramatic difference.
i10 is little expensice comparing Santro, but I feel worth spending it.
Be careful with the service charges when giving for service to the dealer. I had some bad experiences with tridents services and their service charges(for my Santro car). The parts are very costly.
Over all this is a very nice car for a family of 4 members.