To be honest, I don't use the chimney in my kitchen on a daily basis. It's more or less for show now...or only when guests come over and cooking is done. cost me some 19-20K. I just keep happy thinking of the power I'm saving by not using it.
W.r.t hob, if you want one that lies flush with the granite, you will have to cut the marble/granite. So that involves some work but I guess the hob sellers will arrange that for you.
If you have a new kitchen recently done with fancy vaccum pressed membrane shutters 'n all that, the flat hob adds that beauty element to your kitchen. A Pigeon table top stove does not look good in a new kitchen. On the other hand, if you want to save a hell of a lot of money, go for a 500-1000 Rs simple table top gas stove.
Oh, and I don't know about you but I hate the hobs that have 4 burners in a space of 2 feet square. You keep two big pots on the damn thing and you can't use the other burners. A 3 feet hob is far better but I guess that's very costly..maybe 22-25K(I don't know why these things are so costly in India...fleecing I guess)