If you compare both the cars impartially. The Joy is the winner. Its cheaper and has all the features that a Santro Exec GV has. It is up to you, if you want to buy a 700k car or a 550k car that is virtually the same. Mind you, you may suffer by considering lesser things such as resale etc.
For example, Mehran has better resale than a FIAT UNO, people hate the UNO and buy Mehran that is why they suffer throughout the period they continue to drive the Mehran.
Now coming back to the Santro-Joy competition. A good Santro EXEC GV 2004 model costs as less as 450k whereas a Joy 2005 fully loaded costs almost the same which means that Santro is bound to lose more than 200k in 4 years and Joy loses less than 100k in 2 years. Think!