If you turn off data and wifi; It should not drain much. When I first got it, I never turn anything on, my battery level hardly drop, after 5 hours, still got around 90%.
If you notice, the tiles have color and many background is white color; This will consume much battery power. Display is highest battery consumer, although many people thought that processor is the culprit. Process consume power, ONLY if utilized. Many people seems didn't know when left idle or low usage the processor doesn't work at full speed... So, dual core or quad core, is not the problem unless you utilize it at full power.
Android have this battery usage statistics, you will see the highest battery consumer is usually and always the display (unless you have some heavy process running in the background, which you will feel the phone battery is hot).
For Windows Phone, there're actually many things that uses the data/internet; but I'm not sure is it working all the time or how often? With people hub, it's getting live feeds from Windows Live, Facebook, twitter, etc. But I'm not exactly sure how it works, For the live feeds, it seems it only update when you access it? Or does it update frequently? Still unsure about this, but something I do feel the phone is a little bit hot, it seems some hidden process is running.
If it so then why my phone acting so weird eh? when you left ur phone idle of course the display will be turn off after certain time right. So I dont think the display is the main culprit.
Even my iphone 4s only dropped around 5% - 10% max when i left it idle for that kind of time period.