A heat pump proposal usually leads with the equipment. The equipment matters, but the install decides how the system performs and how long it lasts. When you compare two proposals, look past the model line and check the items below.
The sizing record
Ask each installer for the written load calculation that supports the size they propose. A proposal that cannot show its sizing work has not shown you why that size fits your house. Compare the sizing on each proposal against the other. If the two differ widely, ask why in writing.
The outdoor unit location
Check where the outdoor unit will sit, how much clearance it has, how the refrigerant lines will run, and whether the pad or mounting is included. A unit set in a poor location shortens the service you will get from it. Ask each installer to mark the location on a sketch.
The indoor match
Confirm the indoor coil or air handler is listed as a match for the outdoor unit. Ask whether the proposal includes a new air handler or reuses an existing one. If it reuses one, ask who checks its condition before the install.
Defrost and controls
Ask how the system manages defrost and what controls come with it. Ask whether the thermostat is compatible and whether the proposal includes the setup. Controls that are set up poorly are a common source of later calls.
Parts access and service records
Ask whether the installer can source parts for the model you are considering, and how long that usually takes in your area. Ask who provides service after the install and how that service is documented. A proposal that offers no service record is harder to plan around.
Put the install year on record
Whichever proposal you choose, write down the install year, the model, the serial, and the sizing figure from the calculation. That record is what turns the service life guidance on the Heat Pump: typical service life and when to plan page into a real planning date for your house.