I recently sold my 4S and bought an S3. Add me to the list of those who think the S3's battery life sucks.
I have the same amount of push services setup on my S3 as my 4S. I'm not a heavy user at all, typically 1.5-2 hours of total screen time (love that detailed battery usage report in Android), maybe 10-15 minutes of talk on an average day. At the end of the day my battery is at ~35% from a full charge. On the 4S I'll typically be at ~60% with my same usage scenario. I haven't found a suitable replacement app on Android to track my workouts (using it on my iPad now), which would add 90 minutes of constant on on the iPhone on my workout days and I'll still be at 50% on the 4S. On days I'm in NYC with LTE coverage on the S3, forget it. It'll be at <20%. Also my S3 gets uncomfortably hot if I play a certain game for 10-15 minutes, I've never seen the iPhone get that hot. The iphone definitely does more with less compared to Android in general. My S3 is completely stock, with only a handful of apps I installed, FAR less than what I had installed on my iPhone and it was jailbroken. I am still dumbfounded as to how the Engadget test showed 9hrs of usage on LTE..
PS on few occasions where I had 30-60 minutes phone calls, that will be the highest battery drainer for that day, so I agree that the S3's radio is not optimized for voice.