It is not about speed it is about the firmness of the ride and 4000-s offer a much better ride. They still offer good flat protection. Yes they may wear faster but the cost of tires every year or so is not a big factor. If I was using the bike for commuting Gatorskin might be a consideration also I use Gator's in the dead of winter when fixing a flat is a big deal.

The Kool Stop Tire Jack seems like a great tool that I just ordered. Mounting new tires (Gatorskins or 4000-s) on my carbon wheels is very hard and takes way to much time. http://vimeo.com/9173348
http://www.sheldonbrown.com/flats.html#tirelevers