Your question should be, 'Are units with larger living room, bigger bedrooms, etc more difficult to sell?' Consider a 15xx sqft 3 bedder vs a 8xx sqft 3 bedder... would I rather buy a 8xx sqft 3 bedder or pay more for the larger one? Honestly, if the price difference is only a bit higher, I'd definitely go for the bigger units.
Again, this is about supply and demand. All new launches will be looking to shrink room sizes and living room sizes to make home prices look more affordable. In a few years, bigger units will be in higher demand then it'll not be so difficult to sell le... Hmmm...