What is best? Well that comes down to the resulting complexity, cost, performance and other trade-offs. Trade-offs are key as there are almost always significant concessions to be made as you scale up.
So what is my point? Well I guess what I am saying is physical scalability is of course an important consideration in determining what is best. But it is only one side of the coin. What it “costs” you in terms of complexity, actual dollars, performance, flexibility, availability, consistency etc, etc are all important too. And these are often relative, what is complex for you may not be complex for someone else.
I concur—a long time ago I wrote: Complexity is a dimension of scalability.
Original title and link: What Scales Best? ( ©myNoSQL)