Sky Demon v. Pocket FMS
I've been using Pocket FMS for many years now, but I have recently and reluctantly had to concede that Sky Demon is in another league in terms of usability and functionality. PFMS is showing its age, and its interface is bogged down by its evolutionary history. Compared to Sky Demon, its maps are crude, its PLOGs overly-fiddly and complex, and it lacks the excellent implimentation of NOTAMs and weather of SD. True, PFMS is much more configurable (for those that like to fiddle) and it has a Terrain mode like a panel-mount Garmin, which SD lacks. But SD has a vertical elevation view, which is far more useful day-to-day, especially in navigating controlled airspace; it has an excellent position facility - '5 miles NW Le Mans' - which is constantly updated and a great face-saver when ATC unexpectedly asks you where you are, and a printout on the clear, colour-coded PLOG of all the required frequencies. Apparently this last can be achieved by PFMS, but seems to involve more fiddling than I am capable of.
I had hoped that PFMS would rise to the challenge of the new SD upstart but I see no sign that they can make up lost ground, so when my subscription expires I will be heading over to the competition.