In the beginner strategy, the shinespark crash animation does cost time, so it would be faster to Space Jump across the room, as long as you're confident in not falling down.

One thing to watch out for is that the missile pack takes about 10 frames to spawn after the shot block gets destroyed, so in order for Samus' hitbox to touch the missile pack without falling past it, you will generally need to fire your shot at the peak of a jump, or while rising.