If your switcher puts out lots of high-energy broadband noise, you'll play hell filtering it out. That's why it matters.

You shouldn't use a switcher unless you can tolerate the noise it produces. I doubt very much that your eleven-cent filter removes the majority of the ripple from your switcher. Of course, your linear regulator probably does a fair job, though if you used darlington input regulator instead of an LDO, you'd probably have better regulation. You can't do that from a 5-volt supply, though. I wonder how well-regulated that 5 vots is, to the devices that use it. If there aren't any, why use a 5-volt switcher, when a 7-volt switcher might allow better regulation?

It puzzles me that you can design a filter to filter out all the noise from an unknown source. You say the switcher's noise and ripple don't matter. Does that mean that you never looked at it?

RE