If you want the most comfortable casual shoe/Sneaker, I would go with Michael Toschi, specifically with the ones with the Carbon Fiber throughout the shoe. Sometimes you can find them at around 350 or so but don`t be shocked if you see them for around 600 or 700.
Although I think Prada is pure crap as far as their manufacturing goes, I have had a ton of them, their Monte Carlo series are ok for sneakers, especially if you just want a beater.
Also check out Prada Car Shoe for comfort. Car Shoe is A LOT better quality than regular crappy Prada Sport.