The Dual 150 and 160 work very differently from how ADS-B devices handle GPS information, so comparing against a Stratux won't be apples-to-apples. The ADS-B devices send the GPS location information as an ownship report in the ADS-B data which goes directly into your EFB. Since the 150 and 160 don't have ADS-B, they work as an external GPS antenna updating the iOS location service, which the EFB then gets from the operating system.
Apple is constantly changing how iOS handles location data. Most recently, they made it so that if it thinks you're not moving, it stops sending GPS updates, presumably to save power. That causes iFly to report "No GPS Position Lock" until you start moving. Try walking 20 feet while holding the Dual and see if that GPS message goes away and it shows a good signal.