"The ONLY thing I like about 410A over 22 is that in some cases its higher density will allow you to run smaller refrigerant lines. And its also true that 410A is more finicky about installation procedure." The major difference in the two refrigerants has to do with warranty failures. If R-22 systems are not properly installed (pressure tested, liquid line filter dryers installer and a deep vacuum (500 microns vacuum)) the compressor will likely last thru the warranty period. If R-410a systems are installed without proper procedures they will fail prematurely. This is why Carrier would not sell units to dealers that did not go thru proper training. I don't care what system you decide to use. I do believe you should use the most competent dealer in your area. I would eliminate any dealers that are opposed to doing a manual J-8 load calculation as well as opposed to zoning, either by multiple systems or zone controls. I do believe if this is a long-term investment (I would assume this is so if you are looking at the highest SEER systems available) All I know is in 2010 R-22 units will no longer me manufactured!!!!! I dont think I would be willing to install a 19-SEER (check the actual SEER rating) system in my home to save $37.00 per year. When the 10-year warranty ends my system will have been obsolete for 5.5-years! Who will be left holding the bag if you have a problem???? I think TRANE will say that unit is no longer being built!!! LOL!!!
Good luck with what ever you decide to do.
Look http://www.410a.com for info in regards to refrigerant