All three cars are very worthy. They all have good points.
Santro used to be popular, but now its styling is considered old and it is not so good on fuel consumption.
Do not know much about Joy, but, it is also a Korean Car (Daewoo Matiz, under the chevy badge), so, technology in this car won't be much different than Santro.
REVO 105 on the other hand, is not only least priced, but also more bigger in terms of cabin and rear boot size. The 1000cc EFI engine is very robust. The engine is highly reliable, as WULING of China also supplies this engine to many of its GM line-up in China. If GM can trust a WULING engine in its American Branded cars with much of American Technology in them, sold in China, than it must be top class engine.
The people whom have test driven REVO 105 or own it, are very content with its performance. Having said, all the positive stuff, we should not ignore the negatives. Even the best cars, brand new, develop faults in them. German cars are known to have electrical problems, even brand new ones in USA.
In REVO, you can rest assured, the main components, ENGINE and TRANSMISSION are based on very sound and reliable technology, being trusted by GM for its products in CHINA.
WULING also is one of the largest Engine makers of China.
So, REVO 105 is the BEST choice among them all.
Here is the BEST topic on Pakwheels, to find out more in depth about REVO. Contains over 1500 replies.