Well now you see the 410a has no fluorocarbons in it so it doesn't deplete the ozone layer according to the 1980 something protocol, (been too long since I took the test).  I have the same thing in my house, hate it, but had to put up with it at the time, it will get replaced with a lp furnace next time it f,  acts up.  Course the educated bureaucrats determined that our units that hold 5lbs each were the problem and not the millions of pounds that were released every space shuttle launch or thousands every rocket launch.

Rant Over.

As for the 410a, it does do a better job of heating but you dang well better keep the condenser clean in the summer.  Now, are they going to flush it or replace it?

That word "purged," scares me, if it was with anything but nitrogen he's blowing smoke you know where.  I followed the lead of an old boss of mine and told my employees that if I caught them putting anything but oil or refrigerant in a system they could find another place to work.  Since working on systems that get down to -125 to -235 degrees fahrenheit I can assure you nothing beats a deep vacuum.  I can guarantee you that if he filtered the refrigerant coming out and back in, and vacuumed that system to 250 microns, locked it off for 20 minutes, and it didn't  rise more than 200 microns, you will have no problems at all.  The problem with air conditioning guys is a lot of them believe that 500 microns is good enough but I've seen leaks at that level and especially if they use too large of a vacuum pump.  Sadly, it could be the manufacture that recommends it, unlikely for a big name brand though, heck I had one manufacture told me to go buy some Flex Seal to fix a leaky drain pan once!