B for mass pk/RPK, A when u r 1v1ing another sin/EA due to the accuracy evasion and crit u get(it even depends if ur base dex+9 allows u gaining 1% more crit), but basically in 1v1 vs other LA classes use the A if u r apsing and the B if u r DPHing.
It always depends about the situation tho.
EDIT:Forgot to say that im anyway DS fan, Cube aint bad but meh, uno something dead cant hurt u, and when u go full glass cannon u crit 30k just with a TK so yes...I remember cubes and dragon cape were used back in the times mainly for sin 1v1s, but yh cube has been used alot since last patch cuz DPH sins are pretty OP now and u use the cube to kite until u can drop a sweet zerk