a few pointers from my side.hope this helps
1.If you need safety,go for punto.
2.If you need mileage wait till the first reviews and then decide.
3.If you need looks go for Punto.
4.If you need just a powerful engine and does not care about mileage then I would bet on the i20 diesel.
5.If you need better A.S.S go for i20.
6.Punto holds much better upmarket feel than i20.
7.Ride quality and handling is always better in a FIAT.
8.Service being handled by TATA,i would bet FIAT has made sure that GP/Linea needs the least service visits.
9.Personally i would always trust a diesel engine made by FIAT than one from Hyundai.Thats y so many other cars carry the 1.3 MJD.
10.For build quality,a Hyun will NEVER come close to a FIAT.
As for Skoda,its got power and its got good handling but A.S.S is a pain from what i've heard.