Yes, as stated, installation is THE most important part. Of course, equipment brand is important. Some lowball prices are for construction grade equipment (cheap). Trane is a very good brand. (I put a Trane furnace in after I moved in, 2004, and not one issue.) Also, you're getting a top line system, so I would strongly suggest you use the same company to to perform the preseason maintenance checks. There are circuit boards and other high tech gizmos in there, and I would assume that company can service what they sell. I've spent my HVACR career in the commercial/industrial side of the business but have had to work on residential-sized stuff. Plus favors for a couple relatives. I'd be lost on this new inverter drive compressors, but I know my system will need replaced soon, especially the A/C side. I will pay some contractor when/if I need it. I also will insist on all new line set, even if I have to put it in myself. But from what I've seen & heard they do that anyhow. Like LVSteve wrote, the ductwork/air distribution system is very important. Hopefully the salesperson took that into consideration. Although, unless you're on a one story home with basement, you're stuck with what you got.
Good luck, and let us old retired mechanics & service techs know how you like it! FWIW, I, too, will go with a Trane when the time comes.