Which ever one has a choice has it easier.
In most situations, it’s SAHP who are choosing to stay home and therefore they have it easier.
In some situations, one person could stay home but they choose to work because they find that the easier option.
Obviously if you are working a FT job and doing all of the housework, cooking, admin etc on top then it is harder than doing those things without the 40 hour a week job on top.
It is common sense that anything that takes up a big chunk of your time like working, is going to make life and parenting harder.
I find it incredibly difficult having to juggle working FT and parenting, as well as all of the associated tasks.
Being a SAHP is absolutely easier but I love working. So although it’s easier, I wouldn’t say it’s more desirable.
What is easier with SAHPs (apart from having an extra 40 hours a week for housework and cooking etc) is the fact that they have a partner who allows them to do it, by being the one willing to go out to work.
Being financially secure makes life easier, regardless of working/being a SAHP and typically SAHPs are better off financially (else they’d have to work) and therefore they have an easier life because of it.