Okay here is goes:
1.Chery QQ: Not recommended at all
2. Vitz: The best in category, way ahead of others on all respects, specially w.r.t to your point regarding brakes, but will have to install CNG so will be expensive.
- Joy: Okay but comparitively less room and low resale
- Alto VXR: THe only plus point is resale, rest all, its the worst car (brakes handling quality pick and AC, all rubbish comparitively)
You have left out Santro, its okay choice with factory CNG, but brakes sucks. Ac is good
My recommendations:
Vitz, of you can afford and get the CNG installed properly, its the best choice, and parts arte available now, no problems
OR
Santro, Its better than others overall (except Vitz of course) go for FF CNG, Ac is also good, but brakes are not good