Mophie provides little or no protection for the screen - it's flush with the phones face. Thus very easy to break the most fragile part of the phone despite the huge case.
I have also had problems with the durability of the connections. I voted for the OtterBox & SOL.
Does anybody know which of these has the longest battery life? I've set my initial vote but it was mostly based on aesthetics... Will change it once I find more info
@Steve
I copy/pasted the battery lives from each product page. I've also included the weight of each. Important to note some of the cases like the SoL® Hybrid™ Power Pack are also more clunky/bulky then others.
For reference, the iPhone 4 has a 1420 mAh internal battery.
SoL® Hybrid™ Power Pack - 2400maH / 2.3oz
PhoneSuit Elite Battery Case - 2100 mAh / 2.78oz
mophie juice pack air - 1500mAH / 2.5oz
Incipio offGRID Battery Case - each removable battery is 1450mAH /1.9oz
So it looks like the SoL® Hybrid™ Power Pack is the best, plus you have the option of solar charging. But personally I wouldn't sport it due large size (even though it is light).