There has been discussion on AB vs 4DOF.
I realize 4DOF is inputted with more specific details on zeroing, like zeroing weather.
Otherwise they are both quite identical in that they offer either CDM (custom drag model) for bullets with the best twist for it and option to use CDM derivated G1 and G7 BCs.
They both have happy users, so both work.
4DOF has the ratio to move the cdm to better and worse, depending on if you hit higher or lower than predicted. I do not know how 4DOF handles subsonics and the variations there.
AB does this by customizing MV, which many do not prefer, just because MV-temp table is probably hard to set up when you have to lie the values to the software.
After the bullet hits the transonic/subsonic AB offers to use DSF (Drop Scale Factor) that calibrates the bullet flight by fixing the trajectory towards the real hits. This function nobody has a problem with, many wish this could be used for the whole of the trajectory, because they know their MV is 100% true and do not want to enter false values.
In the software section there are differences to AB and Hornady/4DOF Kestrels.
I do not own Hornady Kestrel so I cannot say much about it but I assume it does not have: (take with a grain of salt)
1: Ability to add more cartridge profiles than 3.
AB Elite supports 30.
2. AB Elite has Range Card
3. AB Elite has multiple targets
4. AB Elite lets you edit Zero height and offset ON device.
5. AB supports MV table and AB Elite lets you edit them ON device, but I expect Hornady to have support for it via phone.