A is better as an opening or near endgame as it can leap the minion line and can chase a King easier. I'd prefer A against bots as Destroy is overpowered against bots and the faster mobility is easier to move into position.

I'd prefer B to use in midgame (most of a CEO match) and to use against players as the K move makes it trivial to plan out moves for and makes it easier to defend with.

K and N are pretty equal mobility-wise, so both of these "hollow rangers" would have the same cost. I'd say they both cost 10.