Spiders are very interesting. It's difficult to describe them. I would almost suggest a spider to a new owner simply because their wobble can..well, help us understand what is going on in their heads. My boyfriend calls them "domesticated ball pythons", though that's not really the right word. But I get what he means. They tend to 'communicate' to us more than other ball pythons do.
If I take out my normal and hold him, I know he is stressed. Even when he is not showing signs of stress. I discover his stress later when he refuses to eat, despite him acting completely calm and normal the entire time. Only when he is EXTREMELY stressed out do I notice him acting different than normal.
However, you will know the moment a spider is starting to get nervous. That wobble can speak to us, a lot like a cockatiel's crest. When they get excited, they start spinnin'! I can see when a spider is hungry, and I could probably tell much easier if a spider was going to be willing to take a f/t rodent or if he simply wasn't hungry. If he's not getting excited about the rat, he's probably not going to eat. Sometimes it's harder to tell with the normals who hold perfectly still until they strike--or hold perfectly still....until you leave them alone because they aren't going to eat that night.
Seeing spiders helps me realize how nervous BPs are. I think normals are feeling just as much stress as the spiders are, but the spiders have a way of expressing the excitement, curiosity, fear, or stress in a way that can communicate what they need to us. It's kind of cool to be honest.
Maybe spiders aren't 'adapted to the world' more, but perhaps even 'adapted to captivity' better than a high stress normal.