Upgrading R22 coolant A/C units in rental condo

We have two 15 year old A/C units with R22 coolants in a NYC condo we rent out. We thus don't pay the electric bills. If we upgrade would it be best to replace the condenser units with a new condenser still using R22 (you can still buy these dry and add R22 once installed) or would it make more sense to rip out the old units and replace with a condenser using R410A coolant. The latter would be much more expensive as we would need to change the internal air handler units. I guess something like double the price. Might need NYC permit for the change too. Thanks.