Ivy Bridge is simply a die shrink of Sandy Bridge, which means smaller transistors (granted, it's a ton more complicating than that). Nonetheless, active switching power for the transistors reduces and leakage current is reduced due to the new Trigate transistor structure. This translates to less power consumption and thusly, better battery life (though perhaps marginal in some cases).
The amount of RAM won't really affect your battery power. It's typically insignificant compared to your CPU/GPU/Display/Wi-Fi chip/etc, especially if you're just concerned about 4GB vs 8GB.
Now, if you're pushing 8GB constantly, that means you're probably pushing every other piece of hardware in the machine, thusly overall affecting battery life. But yeah, more often than not, there are other culprits when it comes to power consumption.
EDIT- Sorry, looks like you were looing for a real world example. I don't own one yet, just spewing knowledge/opinion lol