So far I have noticed XXJVU gives the best signal reception almost all over India. I'm from Pune.
I have traveled and used my SGS with ICS and XXJVU all over India(North, East and South) apart from my home town Pune and have got excellent signal reception (-50 dBm to -75 dBm).
Please note that this is over a 2G network of Vodafone. I also have a 3G plan but when I shift to the 3G networks the signal reception starts fluctuating and gives a horrible 1 or 2 bars.
If you are going to use 3G networks in India, you will face issues with signal reception. Most cities in India have horrible 3G connectivity—metros included.
All in all, XXJVU gives me excellent 2G coverage all over India on my SGS i9000 with ICS and Semaphore kernel.
Battery usage is decided by a lot of factors apart from the modem—Kernel plays a major role in battery usage too.