I've been using LCDs for the past six years. No, you're not getting me to use CRTs ever again. I haven't had eyestrain since I ditched the horrid things.

Anyway,

> Running 60Hz animation on a 120Hz refresh CRT would also scroll smoothly, but at the cost of higher CPU use.

How? If you've filled your buffers, execute a blocking vsync() and watch the CPU use drop.

> Which do you think would best achieve the goal?

I think you're worrying too much. This isn't some FPS, so I highly doubt a person will notice 1/120, 1/72, or even 1/50th of a second difference in a side-scroller. Particularly a low-res one.

Games now days don't tie their logic to timed loops or frame rate. You shouldn't either.