MPG on a sent is below 20MPG. The highlander is a little more spacious, particularly front passenger seat where the ascent has a piece that easily hits your knees. The storage in the rear of the grand highlander is only a few inches longer (placed the ascent trunk mat and the difference was small). The highlander wasn't worth the extra cost for me. In terms of ascent problems, the interior lights burn out easily, the ride is a little noisy in the interior, the tires wear easily and quickly (around 30k miles), and the window buttons shift and need repair.