2.5d can have an absolute and definite technical edge when it runs at 60fps and involves extremely fluid animation or is a game where full physics are involved.
LittleBigPlanet would not be possible using sprites - not possible to make a game that moves and feels the same way, or better.
Likewise, no 2D fighting game has animation as smooth as the best 2.5D fighters like SFIV and MVC3 - that's not subjective, it's purely technical. No hand animated game ever made has 60 unique frames of animation for every single movement and transition.
2D animation can give a better artistic impression, like the famous rubbery, stretchy animation in Street Fighter III. But at this point, it's no longer a matter of sprites simply working better for a 2D game; there's tradeoffs in each direction.
Also, I don't really believe that 2D games using 3D engines can't feel or play like a sprite based game; I believe much of this is just perception bias on the part of the players, who are convincing themselves a 2D game is "more responsive". Developers have figured out how to translate snappy control and physics to 2.5D games now; the fact that theres infinite depth perception and softer edges to objects (due in part to z-space depth on those objects) may lead people to believe they're not seeing the same harsh, digital response in controls or collision detection.
Truth is, now that we have high quality 2.5D games around, I can't go back to certain games. I can't play a fighting game with King of Fighters style animation, and Arc System Works' stuff, while having pretty still frames, is pretty fuggly and awkward in terms of animation, leading the gameplay to actually feel more floaty and mushy than it is.
But, some folks seem unwilling to accept that 2.5D graphics just have their own art style and are determined to see them an inferior imitation of "real" 2D graphics.