I apologize for making 2 answers, but I think this one is potentially distinct enough to warrant a second answer. Also, fair warning, wacky speculation ahead.
The natural interpretation of the question is, "What is the simplest view of the nature of our reality?", but in thinking about it more, I keep finding myself tempted to think bigger than "our reality".
What if the simplest program to explain this universe is a program that generates all other programs?
You wanted to compare physicalism to idealism - this is perhaps a type of "idealism", if you can call it that, that resonates with me. And then, this universe is physicalist, but it's physical because "physical universes" are one of the ideas generated by this type of idealism.
So physicalism would be true of this universe, but true on a bedrock of a type of idealism which says "all implementable ideas are implemented".