i generally make a distinction between 'ghost rings' and 'peep sights'. while technically 'peep sights', ghost rings perform much different than a .050" aperture sight.
most of my hunting rifles are scoped but if i had a choice (drilling, tapping, buying ghost rings, dovetailing, matching sights, etc is more cost and time prohibitive than simply scoping it) i would be happy with ghost-ring style sights on all of them except my varmint rifles.
that said i chose 'peep' simply because there was no ghost ring option.