Efficient speakers v. less efficient speakers

I agree with both the above posts. High efficiency speakers can sound more dynamic, colorful, and detailed. The result is better impact and realism.

Sorry I wasn't as clear. I intended my comments to apply to your stated comparison of efficient speaker plus low powered amp versus inefficient speaker plus high powered amp. My experience is that the inefficient speaker plus the high power amp will sound somewhat compressed and lack air and detail. As your original question implies, there is more going on than simple matching of efficiency with power. So, my answer is yes, there is a difference.