Well its good on CNG and drive is excellent. But the main problem is finding a good car which one can keep. As per my experience corolla is a Khota buy one in what ever condition it will still RUN but if you buy a bad condition civic its meant to give you nightmares.
So my Basic Advice is Keep your corolla and Buy a civic and when you are satisfied you got a good piece then Sell the Corolla. IF this option is not possible then Look for a Neat Clean civic which is driven carefully on Petrol and then later get it converted to CNG