Ok, so two questions here:

1)  I know for clan boss, you build up to Warmaster or Giant Slayer.  However, when it comes to arena, is this still the preferred choices?  If not, then what typically is?

2)  I get that the priority should be building to Warmaster or Giant Slayer.  However, of the other two branches, is one typically preferred over the other for something on one branch that is very powerful, or are both branches viable depending on the champion?