I purchased the Skechers Hydrate as well as the Skechers Sleek Fit.  I wanted to get the Hydrate because it was entirely black, whereas the Sleek Fit has white accent stitching.  I actually found that the Sleek Fit looks much nicer in person than the Hydrate.  My co-workers also agreed that it was a cuter shoe.  The Sleek Fit has mesh paneling on the sides, which I can definitely tell is more breathable than the leather on the Hydrate.  The Sleek Fit definitely runs a 1/2 size smaller, but the Hydrate does NOT run small.  I normally wear a size 8.5 or 9, and I ordered both styles in 9.5.  The Hydrate was too big, while the Sleek Fit was just perfect.  If you're also looking at MBT, I suggest the Kaya.  Personally, I thought the MBT Kaya was much more cushioned and had a lot more of the rocker action than any of the Skechers Shape-ups I have tried.