I went from an X45 to an X52 Pro many many years ago. I replaced it last year with another X52 Pro when a rocker switch became intermittent and the stick tensioning spring wasn't doing it's job very well. I stuck with Saitek because my setup works very well for me and overall I am very happy with their hardware and software.
I, like you, expected to have to do re assigning but it wasn't necessary, replacing the X52 Pro with another one was literally Plug and Play as all key mappings and controller IDs stayed the same. I use Saitek hotas, pedal and lever quadrant profiles and most of the keys are mapped through those not via the in game key mapping however those few that ARE mapped through game remained when the new hotas was plugged in and used.
If you are used to Saitek then I would recommend staying with it. I can't say anything about the X56 but all references to the X56 'Rhino' point to it being designed for Space games more than combat aircraft....that put me off as I didn't like the look of it.
Cheerzen