Where most speakers err in speed is the decay more than the attack. Poor decay muddles the sound and affects the next attack plus it reduces dynamics because it creates a higher noise floor for following tones.
For what it's worth, Gordon Holt, the creator of Stereophile and the man responsible for the current form of audio reviewing did lots of live recording. The last speakers he paid for were ATC50a active speakers. He told me they were among the very few speakers that reproduced sound so it sounded like the live performances he recorded. Plus for what it's worth I've always been impressed with ATC speakers, especially the active versions. All things being equal active speakers are superior including transient behavior.