too much complicated answer required for this question. it never be the same conditions. if the original thread starter asks what i think he is asking answer is- they DO in general sound diferent. high eficiency speaker sin general have more lively "imediatly" sound which is always exciting, bass is always tight,but "hard hitting to chest"
never have hear high eficiency speaker with diferent bass- most models differs very litle in this aspect.
low eficiency speakers in general have more reserved and more refined/calm in midrange. bass mostly is punchier, softer and "vibrating stomach"
I find stange coreliation between eficiency and wanting to listening loud- HE speakers can play very loud and clean but for some reason I do not want listen clasical loud with them (rock- maybe)
LE speakers on the other hand are not able to produce so loud sound, and expieenced listener can hear dicorted sound in bass with bass heavy music , but most of them for some sound very calm (in good mean) and realistic on loud levels.