I guess you mean efficient in that they produce a shorter (or even the shortest) sequence of moves to solve a given scramble. But if it takes 5 minutes of computation to produce the solve, then in practice they are not yet very efficient.
Get a faster computer and a larger cube, the trade-off is likely worth it. A rubik's cube isn't such an intractable problem, I doubt a computer can't solve it faster than a human: in the worst case, they can rely on the same algorithm. Then, they can try to find shortcuts or just shorter paths.
I always thought minimizing the number of moves was the goal, hence "more efficient" made sense to me too.