Which region of the world do you live in? Also air-air and air-ground were not an option? These are more readily available.
Anything-to-air wasn’t going to work visually or for occupant comfort. I don’t want refrigeration linesets strung all over the outside, warts on a wall in each room, and after all that having less comfortable heat than hydronic. (On the plus side, it would give AC “for free” [in capital costs].)
Ground source (to water) was my first preference. I’m on a pretty small city lot and the well cost meant for an even longer payback period than an air-to-water heat pump.