I'm no expert, so I don't know why it makes a difference, but it does. Battery drain, when my phone is set to LTE only, versus 3g only (even with mobile data/WiFi off, and phone left untouched overnight - 8 hours) is very different.
It didn't make a difference till 4.4.3/4.4.4. Well, actually, that's not entirely true - when the tower nearest to me wasn't up/running, my phone would hold a weak LTE signal from a distant tower, and my battery life would be miserable even then (when it was set to LTE only versus 3g). After the tower was brought up a few months ago, LTE signal strength improved significantly (approx -95dBm, versus -108dBm or worse earlier), and this problem went away - till 4.4.3 update screwed it up.
Edit: I meant LTE (recommended) vs 3G setting