3G is also less than wifi, especially in areas with weak reception. Wifi on average should always be best, even if a person does the " *#0011# " trick to turn up the mW level of the wifi radio.
To test, compare streaming Netflix or other video sites with 3G compared to wifi. The difference is stunning in areas without great 3G reception. Wifi as far as battery efficiency is tops.
I do not remember the Razr being so different with 3G battery life, so could fit my results that the 3G radio is a little better than the GS3. Odd how the GS3 smokes the Razr for 4G, but weaker for 3G actual results. Sure, the 3G reception can show great dBm, but the results sometimes do no correlate with the GS3. Do not recall the issue with the Razr with 3G.