ReCAPTCHA absolutely hammers Firefox compared to Chrome for me. On sites that use it for login I rarely just get the "check the box" challenge anymore, and am instead being asked to train their CV algorithms by picking 5+ images of stoplights or motorcycles. Punishment for avoiding the Chrome universe I guess.
part of Google's control of captcha also has to do with knowing who you are, so if you come to a site but google knows who you are and have a 99% surety you are not a bot even if you act very botlike on that site you probably aren't going to get any problems.