Answer to this question will depend on
a) Kms driven every day
b) Your love for a petrol or a diesel car
c) Resale value
With diesel prices going up every month and as promised by the Indian Government will continue to go up by Re.0.50/every month till September 2013 for sure. If the government decides to freeze diesel prices post that, then diesel cost will be Rs.52 to 53/litre in Delhi (current prices 50.65/litre). Petrol on the other hand seems to be losing steam. The difference between these fuels was around Rs.27/litre around August - September 2012, which as of today has come down to 13/litre. Market reality today is that the discounts on diesel So if your average daily drive is over 80 kms then diesel still makes sense.
Diesel cars drive quite differently than a petrol car. Diesel engine depict diesel lag, means the car feels like a drag till the RPM at which the turbo kicks, till that time any amount of throttle inputs does get the car moving, noise levels are definitely higher than a petrol car and if you have been driving a petrol car then driving a diesel car would take some adjustment.
India has been a petrol car market till 2012, as dieselisation happened thanks to dramatic rise in petrol prices, petrol became a no go even in used car market. Petrol cars started going real cheap and most of them could not even find a buyer for themselves. Now the story is reverse. In your case since both are different fuel version of the same model and are Toyota vehicles, intrinsically, they get a good price, however, which power plant will be in favour is only a matter of conjecture. Basis toady's scenario and market trends in country like US, where petrol is cheaper than diesel and so is the case in 13 other countries today, I would put my bet on petrol cars ruling the roost 3-5 years from now. So Etios Petrol is what I would buy today.
We at www.ecardlr.com suggest an exhaustive research and test drives of cars in your consideration set. Our inputs are simply suggestions and not a final decision. You must define your need from a car as clearly as possible and only then decide.