At home I have quite a strong 3g signal from t-mobile, between 3-4 bars pretty constantly

GSM signal however is much lower, 1-2 bars.

For battery purposes, would I be better off setting 3G only, or GSM only while at home?

I know in general that 3G is more of a battery hog, even idling, but also know that low signal/drops can be quite a drain as well.

I should note, that networking wise, the device is always on wifi (low power transmit mode) within the house.

I will run some tests on my own, but I'm not quite sure my battery is fully conditioned yet.