As I think about it–and I’ve had this discussion/debate repeatedly–the most important distinction between these two systems is perhaps quite simple. In one system the government controls all property in reality, and in the other only in theory. You have no property rights in Fascism, but at the same time if you keep your mouth shut and do as you are told, you can keep what you have if nobody else needs it. As an example, you have no farm collectivization in Fascism, which alone has caused many, many millions of deaths, including in places like Ethiopia, whose famous famine in the 1980’s was in effect caused by Communists.
John Maynard Keynes, like his mentor George Bernard Shaw, was plainly fine with both systems, but I think temperamentally his inclination was to make de facto control of all means of production less obvious. This is more subtle, and likely more effective in the long run.
In our modern world, I think China is best described as a Fascist state. They no longer pursue collectivized anything, and have rather handed local control of corporate activity over to preferred Party members; control which, however, they view as finally in the hands of the Party, as is all trading policy, capital flows, and monetary policy.