Every right thinking person
hates the disgusting, bloated, abominations that are spiders, big or small

(Well, that goes for all us arachnophobes, anyway, and its probably one of the most common phobias. Though I haven't been so bad since I killed a tarantula on my bed in Cyprus some years ago-somehow, ordinary house spiders seem a lot less threatening after that!)
I think the spiders get the edge, though, because they attack from ambush and/or trap their prey in webs. They have poison (frightening) and to top it off they like sucking their prey dry whilst its helpless-yukk. These are all "horror" elements. I'm with professor Tolkien on this one...