I think I bought some big items from them. I am not hesitant, but I could just be the lucky one.
I have bought and sold AC units online with no issues.
I bought a Mach 8 refurbished for 600 or 800 on eBay and am very happy, it is still like new 3 years later.
Good chance that an AC unit either works or it is in the trash. I not expert, but this is not an item that you can put sawdust into the transmission and get it to work enough to get out the door. Only exception is if there is a slow coolant leak. The units are not serviceable like a car's so a person who could add coolant back to a leaky unit could also fix it!
The only reason to get matching one is for your own personal preferences.