I have the ipad mini 4g version and use both Sky-Demon and Air Nav Pro extensively.
Neither has yet had a satellite drop-out for more than a few seconds - and even this is extremely rare.
I have used it RAM-mounted in a C-152, C-172 and PA-28 Arrow and it has worked like a charm for me.
Remember you don't have to get a SIM for the 4g version, it is not needed for the GPS to function and you will still get the Wi-Fi connectivity when suitable wi-fi coverage is available. You only need the SIM if you are actually going to use the cellular network for data.
Not sure how good the iPhone 5 is at GPS (probably ok) and its connectivity through to the ipad mini (possibly not so good) so can only guess at option 1.
One of my flyer colleagues uses a wifi-version with an external gps receiver and also has no problems.
Last edited by SidT; 31st Mar 2014 at 10:31.
Reason: Added the rareity of satellite drop-out.