I manage the designers, so I'm not the absolute expert. But from what they tell me... there is no real choice (if you're using the Google implementation), it's up to Google on if the eCAPTCHA is shown, and you don't have a choice if it's easy/hard or buses vs. bicycles vs. crosswalks.Are the characteristics up to your choice as a website designer or is it fixed ? What kind of characteristics is that ?
As a non robot internet user, I would be so happy to avoid this nuisance...