As homeowners, what do you think is most important when installing HVAC systems? Do you care about the contractor, the system, the technology behind it, etc.?

Business Management Client Relations
2

All of the above. You must check the License Number and Google search if there are any complaints about the contractor you hire, being insured for Liability & Workers Comp and a written warranty for what he offers.

3

The most important factor will be the contractor. You can always find out about the system and the rest before the purchase takes place. However, the Seers is is what creates the efficiency.
Good luck.

4

All the above and the size of unit. Sometimes it is better to go with a larger unit, that works less and can cool down faster. Also important it the size of ducting and location as heat rises.

5

#1 - Licensed and insured…
No matter what. The most important thing here is that the contractor you hire has to be knowledgeable in what they are selling and installing. If they are not knowledgeable, they are most likely more interested in profit then the client.