HVAC can be predatory. Of course you get the overly pro-business types telling you that its none of you business what man-hour rate is charged by HVAc guys (IME they cloak all their costs and then it comes to an effective $250/hr+) and what profit they make... But that is rubbish. Every other trade that Ive ever dealt with clearly states what theyre doing and what they charge for the effort.
Most residences with central have only a single HVAC system, controlled only by one thermostat (more, newer homes have two or three condensors and HVAC units for better segregation, of course that drives cost). A single central unit limits control - for example, do you want it cold at night to sleep? Why cool off the rest of the house when youre asleep? Window ACs have typically given you more control even if somewhat less efficient on a kWh/ton-hr basis. Still, the amount of time youre using ALL of them might be far less than you think.
I personally do not like Central because of the dust and ducting. This stuff gets dirty no matter what, and ducts have losses regardless of how well sealed and designed they are. I also find that I get allergies and more dry if I am in central versus other approaches to HVAC.
Window ACs have a certain aesthetic element to them that if they are hidden, out of sight, great, but if they are in plain sight, not so nice. Probably also a push-in risk if youre at street level. But they can have their place and the newest units are pushing 12 EER and can be VERY quiet (for good brands like Sharp and Friedrich).
We have split ductless and are able to cool in a controlled manner, space by space, and are far higher efficiency than any central unit (24.5 SEER). They are absolutely silent, unobtrusive in a space, and work wonderfully, as well as let me retain my radiator heat which I prefer (with mod-con boiler and indirect WH for ultimate operating efficiency). A good part of the world also uses these. My inlaws in the Caribbean have had them for years because of the block and open construction, which makes air handlers intrusive and installation of ducts impractical/impossible. They have had great reliability and prefer the efficiency (they are fully self-sufficient via grid-tie solar panels and a diesel generator for hurricanes, but grid prices in the VI are around 52c/kWh).