I have a feeling you will disagree with whatever I say!
I wouldn't know if it is a simpler option in the technical sense, just that it is the common thing to use.
Operation is hands off, though I suspect ASHP is too?
Design seems easy enough - size appropriately. Do people often size ASHP wrong?
Installation - Wouldn't know, plumber makes it look pretty easy and lots of readily available fitters.
Maintenance - The yearly check to keep the 10 year warranty seems pretty quick. What kind of warranty is on ASHP? Bet they don't need yearly inspections?