If it would have been a Diesel, I would have strongly recommended Figo.
But since your requirement is Petrol, and Fabia is not topping the list, my suggestion would be to have Wagon-R, simply because K-Series engines are excellent, compared to Figo's 3-pot engine (or even Fabia's engine).
Wagon-R, because of its structure, also feel spacious, but Figo is definetly more spacious. In my view, Figo petrol is not a sensible choice.
Regarding, extended warranty, though you can get it afterwards, but its always advisable to take at start, specially for cost factor.
More confusion/choices are good for customers. Do bargain, go to different showrooms and take the best deal.