All iPads Wi-Fi signal strength variation across iOS devices

All,

I'm currently in possession of the following iOS devices.

1. iPad 3 LTE
2. iPad Mini Wi-Fi
3. iPhone 4S

All three perform flawlessly when around conventional Wi-Fi networks. Lately, however, I've found myself in an area with quite poor Wi-Fi coverage. I've noticed that the iPad 3 seems to easily outperform the Mini and the iPhone when it comes to signal strength/speed on a weaker Wi-Fi signal. My initial hypothesis is that the LTE plastic "cutout" on the back of the iPad 3 helps with signal reception and/or the larger surface area of the full-size iPad helps to boost its signal reception capabilities.

Has anyone had any similar experiences? I'm curious if someone out there has a better technical explanation, or any advice/experience with boosting signal to iOS devices in weak Wi-Fi coverage.

Thanks for your time.