Speaker sensitivity is not directly related to sound quality. One advantage of higher sensitivity designs is that they can be match with lower output amplifiers. High quality, high wattage amplifiers are much more expensive than mid to low output amplifiers, whereas a high efficiency speaker is no more or less expensive than a similar quality low effieciency design. Remember, any speaker design involves making trade-offs.
low efficiency speaker vs. high efficiency speaker?
What are the advantages and disadvantages of high efficiency speaker vs. low efficiency speaker? Does it mean that 93db efficient speaker will sound better than 86db?