One of the things I loved about Crowley’s ‘Make it four’ comment is the understated admission of the sheer difference in power between an angel (a seraph) and a demon.
When angels first appeared, most demons seemed to be terrified of them, and I think we had a couple of comments indicating that angels hadn’t walked the Earth for thousands of years or something? But then, slowly, angels became a thing like any other, and this always bothered me. I mean, I can understand Crowley’s attitude in dissing Cas and generally making fun of everyone he meets even when those creatures are ten times more powerful than he is (like Dean, Crowley has such a low self-esteem and puts so much care into his BAMF persona as to look almost suicidal), but I also feel most of the time angels are seen as less awesome than they actually are out of plot-related reasons or bad characterization. So, well - the idea that our underhanded and fearsome King Of Hell - someone without any moral qualms whatsover (and let’s go with that) and someone whose powers are magnified by his own position in Hell and three centuries spent amassing knowledge and magical objects - would still acknowledge himself as being worth about one third of a mutilated and guilt-ridden seraph - that makes me very happy.
After all, we all know demons are terrifying; what Supernatural did really well was reminding us of another age-old fact: that angels may be the representation of the divine on Earth, but despite this (or perhaps because of this) they are just as terrifying as demons.