An argument against simulation is that our universe seems gratuitously large. Why have billions of whole other galaxies in it? Given a finite computing budget, you'd expect whoever's running the simulation to want to simulate more planets with civilization and fewer giant dust clouds.
If it is a simulation, it must be doing some very clever lazy evaluation to avoid thinking about every quark in every atom in every star in every galaxy, while still producing results that astronomers can't distinguish from physics on earth.
If it is a simulation, it must be doing some very clever lazy evaluation to avoid thinking about every quark in every atom in every star in every galaxy, while still producing results that astronomers can't distinguish from physics on earth.