Ok, i just did an informal testing of two cases vs. naked. I have two cases:
1. Otterbox Defender (black):
Rugged iPhone 5 case
2. Seidio Active case (with integrated stand) + holster:
SEIDIO | ACTIVE with Metal Kickstand Case for Apple iPhone 5
The prices are actually quite similar. I also tested the iPhone without case (naked).
My house is pretty hard on cell reception. No LTE can enter. Texting without Wifi is pretty rough inside the house (texting pics can take a long time). Certain areas of my house (e.g. my master closet) can be very tough to get cell signal. (My previous phone, Samsung Nexus S 4G, cannot make cell calls inside my house, unless you're standing right next to the certain windows!)
In my master bedroom closet, i made several phones calls to my house phone (land line). I listened for call breakups, static, and drop calls.
Results:
1. Otterbox had minimal call breakups and was able to hold the call throughout. No drop calls nor any significant call breakups that would make the person on the other side of the line not hear more than a word occasionally during conversation. Basically, the calls went smoothly. My wife said that i sounded like i was calling from landline.
2. Naked (no case at all) iPhone came in 2nd. There were significant call breakups but for the most part, the conversation went thru enough to make sense. No drop calls. But, there were times where my wife could not hear a word or two during the conversation. It was kinda rough, but doable in terms of conversation.
3. Seidio came last. I placed 2 calls. Both dropped...one early in conversation...the other dropped after horrible call breakups. It was hard to get a word or two across without breaking up. A few times, it was OK for a few seconds than it would breakup badly. Not workable.
My wife was shock at the result!
This type of result was similar to what i observed with my iPhone 4S Otterbox Defender. Very strange. You would think that the Otterbox with all the plastic and rubber around it would produce the worst result. But, somehow, the combination of hard plastic inside and rubber outside enhances cell reception than the other way around (soft rubber inside and hard outside). And it is also weird that a naked iPhone is not as good as one with Otterbox, esp. when Apple has fixed the antenna issue (since 4S).
Well, needless to say, i am forced to keep my Otterbox Defender because my iPhone is also my work phone AND my pager (when i am on-call).