Client software, in my experience, is no faster, it has to load its "own stuff" before it checks for mail. With webmail I have to open my browser first. A client would have its own update schedule or security fixes that I would need to install. Yes a browser has them as well but I would have to install them even if I had a client. Reliability is not an issue; 95% with webmail is fine. I can not think of one instance where the world would end if I did not send or receive an email.