Harold is right. One of the reasons that Janitrol is cheap is due to their distribution method.
But with any manufacturer what you want to look at is the way the equipment is built and the service, parts and support of the seller.
The main things are: What is it's efficiency. Are the coils (indoor and outdoor) made of copper tubing versus aluminum. The fins are always made of aluminum. Also, you want straight up and down fins, not "christmas tree" fins that look like tinsel wraped around the tubes.
The next thing is the compressor. Does it have a five year or more warranty? Also the controls: does the compressor have an antirecycling lockout. This means that if it detects a fault, it stops and sends you a signal like a red light on your thermostat. Cheap "builder" type units do not have such protection. Noise is also a consideration. Ask the seller what the "sound power level" of the equipmentn is. The testing agency is ARI (the American Rfigeration Institute) in Arlington Virginia.