You should wait and see the results of Qualcomm's new S4 based chips when they start being put in devices later this year. They have been able to embed the LTE modem directly on the die of the chip which according to them will help greatly with both battery life and also performance.
Currently no one else is offering this nor from what i've read has even planned to do this.
MWC coming up at the end of this month and then CTIA a little later after should have some devices with these chips in them and be able to give some better specs on battery life and such.
Signal is everything though too, esp with phones these days. lower signal typically results in lower speeds, which will also in turn make your device work longer to get the same amount of data/information.
