My understanding is that manufacturers overstate their refrigerant benefits, generally suggesting they have the higher efficiency.  There are so many complexities that I expect they are correct in some way.  It’s easy however to find references on the net suggesting R290 has a higher COP than R32 - a bit of Googling gives(link below, its all a bit complicated, no I didn’t read it…):

I think R290 is generally the best choice for a homeowner.  The manufacturer will promote and make whatever they think will sell.  The maintenance/installer would prefer something that cannot burn, and is a controlled substance f-gas (fluorinated hydrocarbon) maintaining their monopoly.

https://www.sciencedirect.com/science/article/pii/S1359431121005007

Like some other posters, I have my doubts about the claim that R290 is less efficient than R32.  There are no references to external sources to evidence this, nor to the claims about R290 resulting in an additional 3 tons per year of CO2 being generated from the additional production of electricity claimed to be required.  

However, the most important (but unmentioned) fact?  That R32 is to be banned as a refrigerant from almost all new heat pump installations by the EU from 2026.  And, given its GWP of 675, that isn’t at all surprising.  Propane would probably have become the refrigerant of choice years ago were it not for the flammability aspect.  That disadvantage has been superseded now by the need to use more climate friendly refrigerants given the urgency of the climate emergency.  In addition, because specialist certification in the handling of refrigerants is not required for R290 installations, potential installers will find it easier to enter the heat pump installation market, installation prices should go down and installation numbers should go up.  Adding to this, as R290 enables heat pumps to run ‘hot’, consumer anxiety about having a cold home through switching technologies will reduce.  Combined with the UK government’s easing of the requirement for insulation standards to be met before grants are given, and a reduced need to install larger radiators for sufficient heat to be emitted, the ingredients may be present for a significant surge in installations.  Energy bills will of course be higher than necessary for those who do not install insulation measures or in some cases larger radiators which may create a new reputational risk for heat pump technology based on running costs rather than it not producing enough heat.  The Government is probably thinking that home owners will later retrofit insulation and larger radiators as necessary.

Manufacturers of R32 heat pumps will be scrambling to introduce new R290 models while desperately trying to offload their R32 stock.  It seems to me that the lower the number of R32 models in use the better.  It’s not for nothing that R32 is being banned, given the millions of new heat pumps that will be installed and their potential for leakage and atmospheric harm.  Finally it seems to me that articles in praise of R32 will please many manufacturers offloading superseded technology, especially when the article has not been updated to mention the ban.

Big flaw in this piece is it assumes electricity for aircon comes from gas fired stations. If its from renewables, the energy does not contribute to gwp.

Indeed we are invvestigating AC at present and are having a survey carried out next month, the need for AC should coincide with our solar panels producing far more energy than the AC will consume - so,although the Panasonic unit we have in mind uses R32, I think our overall performance should be on the side of the angels. Regards, Toodles.