If your phone is one of these:
G502 / G705 / K660 / K850 / W890 / W910 / Z750 / Z770, you should use 2.0 and if it is:
C510, C702, C901, C902, C903, C905, G705, T700, T707, T715, W508, W595, W705, W715, W760, W902, W980, W995, you should use 2.1 flash menus.