I have endless debates with my housemate on this subject. She's terrified of mice but is fine with spiders, I hate spiders but I think mice are pretty cute.
In essence Spiders are the very antithesis of humanity. Their like a black hole, made from weird gray stuff, moving erratically without any sense of purpose: they don't even have a brain.
Mice on the other hand have a beating heart and blood in their veins, I feel that were I able to communicate I could make friends with a mouse, something that would never be possible with a spider.
So Mice > Spiders.