Same performance in CNG,
One thing to note that you maynt find space in the rear boot as the CNG 40 kg used to be installed by the factory. In santro they have a customized cylinder fitted in the spare wheel space.If you switch the car from patrol to CNG you wont feel the difference.
yes you may find more options in chery QQ, they offer DOHC engine, alloy rims, automatic windows, keyless entry i suppose, no air bags and a tachometer. but still its a chinease car and they are asking too much value for its CNG/Patrol version.
Chevy and Joy has almost the same features. No difference.except the CNG cylinder.
What else do you wish to know.
My advise is to check both cars, dont ask the dealers which one is the best and take a decision. yesterday i was checking the indian chevy and they have their own analysis about the maintance comparsion on 4 cars, Joy was #1. it may help you.Try it.
if you need any help or answer let me know.