HVAC installers in Chicago

[Tim Coppola]

I'm looking to replace both HVAC units in my building. I've had a few companies come out and give estimates varying from $8,732 to $11,236. I've read that while the brand does matter the installer matters just as much if not more. Is this true?

I've pretty much narrowed my choice down to two companies, Besco Air which uses Rheem and Air Blue which uses Carrier. 

Any suggestions or advice would be much appreciated.

Thanks in advance,

Tim