[Plugin: WP Super Cache] Emptying cache from CRON on MU site?

I would like to empty my WP Super Cache for all blogs on my MU install every 24 hours. I’ve read that a good way to do this is to setup a cron job that calls:

wp_cache_clear_cache();

Sadly this is not working for me, and I’m not clear on exactly what that function does. Is there any reason that I should NOT simply write a shell script that does:

rm -rf /path/to/cache/blogs/*
rm -rf /path/to/cache/supercache/*

If this is a bad idea, why? What would be the correct way to accomplish this goal?

Thanks,
Gabe