Hi Sylvie,
I have done (permutations of) both of these trips and if my lottery numbers came up (must buy a ticket!) I would be back to India like a shot.
The "Marigold" celebs have certainly done their bit to push India but, as Bob says, it is an assault on the senses - even sometimes if you are used to touring holidays.
Out of the two trips you have highlighted then, for your first tour, China would perhaps be the better option.
However, if you are being pulled to India then Kerala should not be overlooked. You get India but at a much more genteel pace and that would serve as a good introduction to the north of India at some future date.
Best, Ian.