It depends on what you're planning on using the sword for. If you are going to solo grind much, then put the relevant license(s) on for faster kills. Otherwise, Ice ViVi licenses can give +1% crit to the weapon and it is the fastest to kill amongst your other options =/
Personally I think the lv 30-40 range passes rather quickly that spending time grinding up any license is a waste of time. With the exception of +9 lv 30 weapons, in which case put on... an Orc License would be a good idea
