You have tried a lot of them and then you recommend one that you haven't tried out ?!
Are you saying you own both the ESPOW and Spark tablet case you linked?
I'm not in the market for a solar charger for an iPad so no I don't have one, unless you're in a location where AC power is not accessible I feel that most of these solar things are a waste of money. I've tried a lot of products for my iPhone and have a good idea of what's more of a gimmick than anything.
However "if" I was, the one I linked is the one that appears to makes the most sense (at least via specs and corresponding product videos). It doesn't appear to make outrageous claims and his results (based on raw sunlight, solar efficiency rating, amp rating/voltage and time) appear very realistic. However even then, the OEM AC adapter will still charge my iPad faster, weigh a lot less, take up less room in my bag and cheaper (comes with the iPad).
I suggested a realistic solution if "solar" is of the main concern and interest. Both of your suggestions would be bad choices in my book. First off both of those units use both a small, very inefficient solar panel (often too small for an iPad, esp an iPad 3) and incorporate internal batteries. You will end up having to charge it mostly on AC power (because the sun takes too long) which defeats the purpose of buying a solar product in the first place. You'd be better off buying the battery portion and save a few bucks if that's the case. The thought of putting out a black leather iPad case out in the sunlight for the majority of the day trying to gather sunlight is appalling, where I am where sunlight is abundant, the sun will trash the Spark case in no time.
If you don't believe me, why don't you buy those units, drain the battery down to zero, then put them in the sun to charge and report back with the times.
