If you have too many rifles, you end up shooting reloads.
However, in developing loads for absolutely new calibers, I shoot factory, and reloads over a chronograph. I want my reloads to be close to factory velocities, assuming that the factory loads provide the performance I want.
Of course I examine on paper performance, and once I get a reload that is acceptable, that is what I will use.
Factory ammunition is expensive, maybe with premium bullets I might stick to factory, but in most cases, I get Nosler partition bullets, or equivalent, and reload my own.