Well you're not just extracting sugars from the grain, and not all the sugars you extract are fermentable, so it isn't quite as straight-forward as higher efficiency leads to more alcohol and less malt flavor. However, I think of it like this... there is a maximum number of IBUs you can extract from bittering hops, 80-100-ish. So one school of thought is that if you add more hop material to get calculated hops over 100, you're just wasting hops. Rubbish. Hop up a DIPA to 200 IBU or so, and you're going to have a drastically different beer than if you only hopped it to 80 IBU. There's more than bitterness that gets extracted, but flavor, aroma, mouthfeel from all those little hop particles floating around in your beer, foam from the proteins extracted, etc.
So in that sense, if you make a beer with 95% efficiency to get a 1050 wort, and then scale up the recipe and hit the same gravity but at 65% efficiency, you're going to use a LOT more malt at 65% efficiency. Will they be exactly the same beer? Too many variables to say, but my confirmation-biased opinion is that the quality of my beers suffers a bit when efficiency jumps up over 85% or so.