I'd rather have the tarantula than roaches, although smaller spiders bother me a bit. Something that I've come to realize is that quite often, it's the little critters that pack the biggest punch, when it comes to venom. Bigger critters can often overpower their prey. That's the case with some of the nastyer spiders, like the wolf and brown recluse, as well as with scorpions. If a scorpion's got big pincers, it's probably not as venomous as one with smaller pincers.
Mark
Oh, and I also LOVE to watch the little jumping spiders. They're tiny, but often colored really brilliantly. They're just fun to watch.
Mark