Hey Mike
Mate i own and love the SBS-1e by Kinetic easy to use, lightweight and portable for travel use. but i believe is a much more powerful device compared to the airnav i have not used it but i have read the aerial does not pick up as much as the standard one that comes with the SBS.
Software with the SBS is very light on memory so you do not have to worry about the program.
I hope this helps. please don't be afraid to email me
mattcoughran@gmail.com if you would like screenshots or photos of the device im more then happy to provide.
Cheers Matt