Qt 4.8.5 or 5.1?

Hi All, I am currently using Qt 4.6. There are several issues I faced in 4.6 like restoring window and state etc. Now thinking to update Qt version but getting confused which version should I opt for Qt 4.8.5 or 5.1 ? Could you please help me to decide which version should I update. I am using qt with visual studio.