I'd be interested in seeing the results of a head-to-head comparison of all the various ballistic software out there in terms of consistency. If you enter the same data to each program, you should get the same output data. Be interesting to see if that actually happens...then it just becomes shooter preference for the UI and platform.
I'm using a Trimble Recon with Horus ATrag MX and Patagonia Cold Bore. I also have a Kestrel with Horus in it. Haven't wrung out the programs yet to see which I like more.
Still trying to find an interface cable for my Vector 21's for less than $400. And sadly my Recon doesn't have bluetooth. I'm getting Trimble GPS CF card for it and may pick up a Bluetooth card as well, if I can hook it up to the Kestrel.
I prefer the Recon because it's ruggedized. iPhones and Droids are not what I'd call field-rated electronics, although I do have Istrelock on my iPhone just in case.