Which AC Unit to Choose?

[Mathuw Chandler]

I have to replace the HVAC system in my home.  This is a two family flat one unit up one down, i will be living in and replacing the downstairs unit.  I have narrowed my bids down to two, one includes a Coleman brand AC unit the other Carrier unit. I have heard of Carrier before, mostly due to their marketing but not Coleman. 

Location: St Louis, Coleman bid is cheaper.

1) can anyone give me some advice on which to pick, does anyone have any insight on these brands?

2) does it matter more who installs it?  does the company installing it matter more than the actual unit?