Santro
Pros :
Looks kool, better than cultus
Economical, very good mileage
EFi
AC is excellent
Quickest car in its category
Trims with power steering/windows are available
Cons :
Car has high center of gravity, therefore more likely to flip.
Resale isn't so good as cultus.
Spares are harder to find then cultus.
Its a discontinued car.
Cultus
Pros :
Parts are easily available
Parts are cheaper than that of santro
Available with variants including power steering/windows
Resale is good, better then santro
More aerodynamic shape then santro
Running cost is a cheaper, i think it requires less care and maintenance.
Cons:
AC SUCKS!
Quality wise its weaker then santro
shape is blehhh and has been the same since quite a few years!
Thats all i can come up for now.
To help decide which car you want, you should tell us for how long you are planning to keep the car, whats your range and priorities.