There are, even in the same browser, there is also a difference. If you alter your settings in the UCweb, then you can comfortably log in and out of PM but if you leave it with the default mode, you are only risking your account being blocked.
It won't be blocked it will ve unable for you to log in, in the sense that they believe that on that mode Ucweb are being able to recieve our data and first compress it before we logging in and that dangerous. Well, they know better but all what I know is that I can log in with my UCweb with no problem, though they are very secured with the pin being sent to our mail whenever we wanna login.