I use them on all out of town trips, which is 95% of my riding. Like the guys above, I want to save what's left of my hearing. I should have used them back in my loud electric guitar days...
Anyway, I've had several different full face helmets, and don't find any of them to be quiet enough to take out the wind noise, so it's ear plugs all the way.
I don't care which kind I use, so usually the cheapest I find. Like Red01, my employer (me) buys them by the box, so I always have ample supplies.